How Climate Affects Skin: Protection Tips for Every Weather

Climate can affect your skin in ways that are easy to overlook. While choosing the right cleanser, moisturizer, sunscreen, or serum is important, the environment around you can also influence how your skin looks and feels.

Changes in temperature, humidity, wind, sunlight, altitude, and air quality may affect skin dryness, oiliness, comfort, and sensitivity. For example, cold and dry weather can contribute to dryness and irritation, while hot and humid conditions may make the skin feel oilier and sweatier.

Understanding how climate affects skin can help you make more practical decisions about your skincare routine. Instead of using exactly the same products throughout the year, you may need to adjust product textures and routines as environmental conditions change.

This guide explains how different climates and weather conditions can affect the skin and provides practical tips for protecting your skin in hot, cold, dry, humid, high-altitude, and polluted environments.

 

How Climate Affects Your Skin

Your skin is the body’s largest organ and performs several important functions. It acts as a protective barrier between your body and the outside environment, helps reduce excessive water loss, contributes to temperature regulation, and provides sensory information.

Because the skin is constantly exposed to the environment, changes in climate and weather can influence how it looks and feels. Factors such as temperature, humidity, wind, sunlight, and air quality may affect skin comfort and can contribute to dryness, oiliness, irritation, or other changes.

Temperature and Oiliness

Hot weather can make the skin feel oilier, particularly when increased sweating combines with natural skin oils. Some people may also notice that their skin becomes shinier or more prone to clogged pores during hot weather.

Humidity and Skin Moisture

Humidity describes the amount of water vapour present in the air. Dry air can contribute to increased water loss from the skin, which may leave the skin feeling tight, rough, or flaky. In contrast, higher humidity may reduce the rate at which water evaporates from the skin’s surface.

Wind and the Skin Barrier

Cold or windy conditions can be particularly uncomfortable for the skin. Environmental exposure may contribute to dryness and irritation, especially when the skin’s protective barrier is already compromised. A healthy skin barrier helps retain moisture and reduce exposure to potential irritants.

Sunlight and Environmental Exposure

Ultraviolet (UV) radiation can damage the skin, regardless of whether the weather feels hot or cold. Over time, excessive UV exposure can contribute to premature skin aging and increase the risk of skin cancer. Other environmental factors, including air pollution, may also contribute to oxidative stress and inflammation.

Paying attention to these environmental changes can help you adjust your skincare routine when needed. Rather than waiting for your skin to become extremely dry, irritated, or uncomfortable, you can make small changes to your routine as the climate and seasons change.

 

How Different Climates Affect Your Skin

Each climate has its own set of problems. We will deconstruct the most typical environments and how each of these will affect your skin.

Hot and Humid Climates

Hot and humid weather can change how the skin feels and may make some skin concerns more noticeable. Higher temperatures often increase sweating, while humid air can make sweat evaporate more slowly. As a result, the skin may feel sticky, shiny, or uncomfortable.

Increased Sweat and Oiliness

During hot weather, the body produces sweat to help regulate body temperature. When humidity is high, sweat may evaporate more slowly, leaving the skin feeling damp for longer periods.

Natural skin oil, known as sebum, can also contribute to a shiny appearance. For people with oily or acne-prone skin, the combination of sweat, sebum, sunscreen, and other products may make the skin feel heavier during hot and humid conditions.

Clogged Pores and Breakouts

Sweat does not directly cause acne, but hot and humid conditions may contribute to factors that make clogged pores more likely in some people. Sweat, sebum, dead skin cells, and certain skincare or cosmetic products can build up on the skin’s surface.

Acne is a complex condition influenced by several factors, including excess sebum, clogged hair follicles, inflammation, and the activity of Cutibacterium acnes. For a broader look at the factors that contribute to acne and ways to manage it, see our guide to acne causes, treatment, and prevention. If breakouts become persistent or severe, it may be helpful to speak with a dermatologist.

Yeast-Related Folliculitis

Warm and humid environments can also create conditions that may contribute to certain yeast-related skin problems in susceptible individuals, including Malassezia folliculitis.

Malassezia folliculitis can sometimes resemble acne and may appear as small, similar-looking bumps that can be itchy. Because several skin conditions can look alike, persistent or itchy bumps should not be self-diagnosed. A dermatologist or qualified healthcare professional can help identify the cause and recommend appropriate treatment.

Hot and Dry Climates

Hot and dry environments can place different demands on the skin than hot and humid climates. Low humidity, strong sunlight, and dry winds can contribute to moisture loss and may leave the skin feeling tight or uncomfortable.

Increased Moisture Loss

When the surrounding air is very dry, water can evaporate more readily from the skin’s surface. This process is related to transepidermal water loss (TEWL), which refers to the movement of water through the skin and its evaporation into the surrounding environment.

In dry conditions, increased moisture loss may leave the skin feeling tight, rough, dry, or flaky. These effects can be more noticeable when dry outdoor conditions are combined with air conditioning or other indoor environments that have low humidity.

Skin Dryness and Irritation

When the skin becomes very dry, its protective barrier may become less effective. This can make the skin feel more sensitive and may contribute to symptoms such as redness, itching, or stinging.

People with naturally dry or sensitive skin may notice these changes more easily, particularly when they are exposed to dry air for long periods.

Sun Exposure and Skin Damage

Hot and dry climates are often associated with strong sunlight and frequent outdoor exposure. However, it is ultraviolet radiation rather than temperature itself that damages the skin.

Excessive UV exposure can contribute to sunburn, premature skin aging, changes in skin pigmentation, and an increased risk of skin cancer. Using appropriate sun protection is therefore important, particularly when spending extended periods outdoors.

Protecting the skin from excessive UV exposure is also an important part of maintaining a healthy-looking complexion over time. For more practical advice on managing dry skin during colder months, see our guide to winter skincare tips to prevent dry skin.

Cold and Dry Climates

Cold and dry weather can be particularly challenging for the skin. Low humidity, cold winds, and dry indoor heating can all contribute to moisture loss and leave the skin feeling dry or irritated.

Effects on the Skin Barrier

The skin’s outer barrier helps retain moisture and protect against external irritants. Cold, dry conditions may contribute to increased dryness, particularly when the skin is also exposed to wind or heated indoor air.

When the skin becomes very dry, it may feel tight, rough, or uncomfortable. In some cases, dryness can also contribute to visible flaking, cracking, or irritation.

Dryness, Redness, and Skin Conditions

Cold and dry weather can aggravate dry or sensitive skin. People with conditions such as eczema or rosacea may also notice that their symptoms become more difficult to manage during certain weather conditions.

However, climate affects people differently. Some individuals may experience significant dryness during winter, while others notice only minor changes. A skincare routine may need to be adjusted based on how your own skin responds.

Dull or Rough-Looking Skin

When the skin becomes dry, dead skin cells can accumulate more noticeably on the surface. This may make the complexion appear rough, dull, or uneven.

Gentle cleansing and regular moisturising can help support the skin barrier. It is generally best to avoid over-cleansing or using harsh exfoliating products when the skin is already dry or irritated.

Cold and Humid Climates

Cold and humid climates can affect the skin differently from cold and dry environments. Higher humidity may reduce the rate at which water evaporates from the skin’s surface, but cold temperatures, wind, and frequent exposure to wet weather can still leave the skin feeling uncomfortable.

Cold Wind and Skin Irritation

Cold wind can be harsh on exposed areas of the skin, particularly the cheeks, nose, and lips. Prolonged exposure may contribute to dryness, redness, chapping, or a burning sensation in some people.

Protective clothing, such as scarves and other weather-appropriate coverings, can help reduce direct exposure to cold winds.

Changes in Skin Comfort

Even in a humid climate, skin can still become dry or irritated because temperature, wind exposure, indoor heating, and individual skin conditions also play a role.

If your skin feels dry during colder months, you may benefit from using a gentle cleanser and a moisturiser that supports the skin barrier. People with sensitive skin may also find it helpful to avoid using too many exfoliating or potentially irritating products during periods when their skin feels uncomfortable.

High-Altitude Climates

Higher-altitude environments can present additional challenges for the skin, particularly because ultraviolet (UV) exposure generally increases with altitude. Outdoor activities such as hiking, skiing, and mountaineering may therefore increase the importance of protecting the skin from prolonged sun exposure.

Increased UV Exposure

At higher altitudes, there is less atmosphere above you to absorb and scatter ultraviolet radiation, so UV exposure generally increases with elevation. This means UV exposure can be stronger than it is at lower elevations.

Snow can reflect UV radiation and increase exposure to reflected sunlight, which is particularly important during skiing and other outdoor winter activities. For this reason, sun protection is important at high altitude even when the temperature is cold or the surrounding landscape is covered with snow.

Dry Air and Skin Comfort

High-altitude environments can also have dry air, which may contribute to increased moisture loss from the skin. Some people may notice that their skin feels tighter, drier, or more sensitive after spending time in these conditions.

Using a suitable moisturiser can help support the skin barrier, while regular sun protection can help reduce exposure to harmful UV radiation. Lip balm with sun protection may also be useful because the lips can be particularly vulnerable to cold, wind, and sun exposure.

Urban and Polluted Environments

People living in urban areas may be exposed to environmental pollutants from sources such as vehicle exhaust, industrial activity, smoke, and airborne particles. Research has explored how air pollution may affect the skin, although the effects can vary depending on the type and level of exposure as well as individual skin characteristics.

Pollution and Oxidative Stress

Airborne pollutants can settle on the skin’s surface and may contribute to oxidative stress and inflammation. Over time, environmental exposure has been associated with changes in skin appearance, including uneven skin tone and signs of premature skin aging.

However, pollution is only one of many factors that can affect skin health. Sun exposure, smoking, genetics, age, skincare habits, and underlying skin conditions can also play important roles.

Skin Dullness and Irritation

Exposure to dirt, sweat, oil, and airborne particles may leave the skin feeling dirty or congested. Some people may also experience irritation or worsening symptoms of existing skin conditions.

A gentle and consistent cleansing routine can help remove sunscreen, sweat, oil, makeup, and other particles that accumulate on the skin during the day. However, excessive cleansing or using harsh products can also irritate the skin, so it is important to choose products that suit your skin type and sensitivity.

 

How the Seasons Can Affect Your Skin

You do not have to move to a different climate for your skin to notice environmental changes. Temperature, humidity, sunlight, wind, and indoor heating or cooling can change throughout the year, and your skincare needs may change with them.

Summer

Hot weather can increase sweating and may make the skin feel oilier, particularly in humid conditions. Sun exposure can also be greater when people spend more time outdoors.

During summer, a comfortable routine may include a gentle cleanser, a lightweight moisturiser if needed, and broad-spectrum sunscreen. If you spend time outdoors, consistent sun protection is important even when conditions are cloudy. For more guidance, see our guide to daily sunscreen on cloudy days.

Winter

Cold weather and low indoor humidity can contribute to dryness and irritation. Wind and indoor heating may make these effects more noticeable.

During colder months, some people may prefer a richer moisturiser and a gentle cleanser to help maintain skin comfort. Sun protection is still important when exposed to UV radiation, including during outdoor winter activities.

Spring and Autumn

Spring and autumn can bring changing temperatures and humidity levels. Your skin may respond differently as conditions change, so it can be helpful to adjust your routine gradually rather than replacing every product at once.

For example, you might use a lighter moisturiser when the weather becomes warmer or choose a richer formulation when cooler, drier conditions return. The best approach depends on how your own skin responds to the changing environment.

How to Protect Your Skin in Hot Climates

Hot weather does not mean you need to stop moisturising your skin. The goal is to choose products that feel comfortable in the heat while maintaining a simple and consistent routine.

Choose Lightweight Moisturising Products

If your skin feels greasy or heavy during hot weather, consider switching to a lightweight lotion or gel-cream. Ingredients such as glycerin and hyaluronic acid can help attract and retain water in the skin, while ingredients such as squalane can provide emollient benefits without necessarily requiring a heavy cream texture.

Choose products based on how your skin responds rather than assuming that every person in a hot climate needs the same formulation.

Protect Your Skin From UV Radiation

Use a broad-spectrum sunscreen with an SPF of 30 or higher on exposed skin when you will be outdoors. Choose a water-resistant formula when swimming or sweating heavily, and follow the product’s directions for reapplication.

Sunscreen works best as part of a broader sun-protection strategy that can also include seeking shade, wearing protective clothing, and limiting prolonged exposure to strong sunlight.

Manage Sweat and Excess Oil Gently

After heavy sweating, gently cleansing the skin can help remove sweat, oil, sunscreen, and other buildup. However, repeatedly washing the face or using harsh cleansers can irritate the skin.

If you are prone to clogged pores or acne, a product containing salicylic acid may be useful for some people. Start gradually and follow the product instructions, particularly if you have sensitive or dry skin. If irritation develops, reduce use or stop the product.

Blotting papers can also be used during the day if you want to reduce surface shine without repeatedly washing your face.

How to Protect Your Skin in Cold Climates

Cold weather can make the skin feel dry, tight, or irritated, especially when low humidity, wind, and indoor heating occur together. A few simple changes can help maintain skin comfort during colder months.

Use a Richer Moisturiser When Needed

If your usual lightweight moisturiser no longer keeps your skin comfortable, consider switching to a cream or other richer formulation. Look for products containing ingredients such as ceramides, glycerin, petrolatum, or other emollients and occlusives that help support the skin barrier and reduce moisture loss.

You do not necessarily need a heavy moisturiser simply because it is winter. Choose a texture that keeps your skin comfortable without causing problems such as excessive greasiness or clogged pores.

Support the Skin Barrier

Cold, dry conditions can make already-sensitive skin more uncomfortable. A gentle cleanser and regular moisturising can help support the skin barrier.

If your skin is dry or irritated, avoid introducing several strong active ingredients at the same time. Products containing exfoliating acids or other potentially irritating ingredients may need to be used less frequently if they make your skin feel uncomfortable.

Continue Sun Protection

Sunscreen is not only for hot summer days. UV radiation can still reach your skin during winter, particularly when you spend time outdoors.

If you are outdoors for extended periods, especially at higher altitudes or around snow, use a broad-spectrum sunscreen with SPF 30 or higher on exposed skin and reapply according to the product’s directions. Protective clothing, sunglasses, and shade can provide additional protection.

If your winter sunscreen feels drying, you can choose a formulation that also provides moisturising benefits rather than skipping sun protection.

For more practical advice on managing dry skin during colder months, see our guide to winter skincare tips to prevent dry skin.

How to Protect Your Skin in Dry Environments

Dry air can increase moisture loss from the skin and may leave it feeling tight, rough, or flaky. This can happen outdoors in arid climates and indoors when heating or air conditioning lowers humidity.

Use Moisturising Ingredients

Humectants such as glycerin and hyaluronic acid help attract and hold water in the outer layers of the skin. They can be useful ingredients in moisturisers and other hydrating products.

If you use a hydrating serum, applying moisturiser afterward can help support the skin barrier and reduce moisture loss. You do not need to use a separate serum if a moisturiser already provides enough hydration for your skin.

Add an Occlusive When Extra Protection Is Needed

Occlusive ingredients help form a protective layer on the skin’s surface, reducing water loss. Examples include petrolatum and dimethicone.

If your skin becomes particularly dry, applying an occlusive product over a moisturiser can provide additional protection. However, the best product and texture will depend on your skin type and personal preference.

Consider Using a Humidifier

If indoor air is very dry, a humidifier can increase moisture in the surrounding air and may make the environment more comfortable for dry skin.

If you use one, clean and maintain it according to the manufacturer’s instructions. Poorly maintained humidifiers can allow microorganisms or mineral deposits to accumulate and become dispersed into the air.

A humidifier is an optional tool rather than a requirement. A consistent moisturising routine and avoiding unnecessarily hot water or harsh cleansers may be just as important for maintaining skin comfort.

How to Protect Your Skin in Humid Environments

High humidity can make sweat evaporate more slowly, leaving the skin feeling sticky or oily. Some people may also notice more clogged pores or breakouts, while others may experience little change.

Choose Comfortable, Lightweight Products

If heavy skincare products feel uncomfortable in humid weather, consider using lightweight lotions or gel-creams. Products labelled non-comedogenic may be worth considering if you are prone to clogged pores, although no product can guarantee that breakouts will not occur.

There is also no need to avoid every oil or butter simply because the weather is humid. Different ingredients and formulations affect people differently, so choose products based on your skin type and how your skin responds.

Keep the Routine Simple

Using several layers of heavy products may make the skin feel uncomfortable in humid conditions. A simple routine consisting of gentle cleansing, appropriate moisturising, and sun protection may be sufficient for many people.

If you sweat heavily during the day, gently cleansing the skin afterward can help remove sweat, sunscreen, and excess oil without repeatedly scrubbing or washing the skin.

Consider Antioxidant Ingredients

Antioxidant ingredients such as vitamin C and niacinamide are commonly used in skincare and may provide additional benefits depending on the formulation and your individual skin needs.

However, they are not a substitute for sunscreen or other sun-protection measures. If you already have a routine that works well for your skin, there is no need to add an antioxidant serum solely because the weather is humid.

How to Protect Your Skin in Polluted Areas

If you live in an area with significant air pollution, a simple and consistent skincare routine can help keep your skin clean and comfortable. Pollution is only one environmental factor affecting skin health, so the goal is to avoid unnecessary exposure while maintaining the skin barrier.

Cleanse Gently

At the end of the day, gently cleansing your skin can help remove sunscreen, makeup, sweat, excess oil, and particles that have accumulated on the skin.

Double cleansing may be useful for people who wear makeup or water-resistant sunscreen, but it is not necessary for everyone. For some people, one gentle cleanser may be enough. Over-cleansing can contribute to dryness and irritation, so choose an approach that suits your skin.

Consider Antioxidant Skincare

Antioxidant ingredients such as vitamin C are commonly used in skincare because they can help counter oxidative processes in the skin. If you’re interested in learning more about vitamin C in skincare, see our guide to vitamin C serum benefits for glowing skin. Some people may choose to include an antioxidant serum as part of their routine.

However, antioxidant products should be viewed as an optional addition rather than a protective shield against pollution. They do not replace sunscreen, gentle cleansing, moisturising, or other measures that help protect the skin.

Protect and Support the Skin Barrier

A healthy skin barrier can help the skin tolerate environmental exposure more effectively. Use a moisturiser that suits your skin type, particularly if pollution, weather, or frequent cleansing leaves your skin feeling dry or irritated.

If you experience persistent redness, itching, painful breakouts, or other skin changes that do not improve with basic skincare, consider consulting a dermatologist or other qualified healthcare professional.

How to Protect Your Skin at High Altitude

High-altitude environments can expose your skin to stronger UV radiation and, in some locations, dry air and cold winds. If you are spending time outdoors at elevation, especially while skiing, hiking, or climbing, your skincare routine should include reliable sun and weather protection.

Use Broad-Spectrum Sunscreen

Apply a broad-spectrum sunscreen with an SPF of 30 or higher to exposed skin before spending time outdoors. SPF 50 can be a useful choice for prolonged outdoor activities or intense sun exposure, but proper application and reapplication are also important.

Reapply sunscreen according to the product’s instructions, particularly after sweating, swimming, or wiping your face. Snow can reflect UV radiation, so do not assume that cold temperatures or cloudy conditions eliminate the need for sun protection.

Protect Your Lips and Exposed Skin

The lips and other exposed areas can be vulnerable to sun, wind, and cold. A lip balm with sun protection can help protect the lips during outdoor activities.

Hats, sunglasses, protective clothing, and seeking shade when possible can provide additional protection from UV radiation and harsh weather.

Moisturise Dry Skin

If the air is dry or your skin feels tight, use a moisturiser that helps support the skin barrier. Products containing humectants, emollients, or occlusive ingredients may be useful depending on your skin’s needs.

If your skin becomes very dry or irritated, keep the routine simple and avoid introducing several new or potentially irritating products at the same time.

Universal Tips for Protecting Your Skin in Any Climate

Although skincare needs can change with the weather, a few basic habits are useful in almost every environment. The goal is to maintain a healthy skin barrier, protect against UV radiation, and avoid unnecessary irritation.

1. Drink Enough Fluids

Staying adequately hydrated is important for overall health, particularly in hot weather or when you are physically active. Hydration is only one part of supporting healthy skin. A balanced diet that provides a variety of nutrients is also important for overall skin health. For more information, see our guide to foods for healthy skin. However, drinking extra water is not a guaranteed treatment for dry skin. Environmental conditions and the condition of the skin barrier also affect how dry or comfortable your skin feels.

2. Adjust Your Routine When the Weather Changes

Your skin may need different textures or levels of moisturisation as temperature and humidity change. A lightweight moisturiser may feel more comfortable during hot weather, while a richer formulation may be useful when conditions become cold and dry.

Make changes gradually rather than replacing your entire routine whenever the weather changes.

3. Know Your Skin Type and Pay Attention to Its Response

Knowing whether your skin tends to be oily, dry, combination, or sensitive can help you choose suitable products. However, your skin can also change with age, seasons, medications, and environmental conditions.

Pay attention to how your skin responds rather than relying only on a fixed skin-type label.

4. Protect Your Skin From UV Radiation

Sun protection is important regardless of whether the weather feels hot, cool, dry, or humid. When exposed to sunlight, use broad-spectrum sunscreen with an SPF of 30 or higher and combine it with shade, protective clothing, and other sun-protection measures when appropriate.

5. Avoid Over-Cleansing and Over-Exfoliating

More cleansing or exfoliation does not necessarily mean healthier skin. Excessive use of harsh cleansers, scrubs, or exfoliating products can contribute to irritation and dryness.

Use gentle products and adjust the frequency of exfoliation according to your skin’s tolerance and the instructions for the product you are using.

6. Patch Test New Products When Appropriate

If you are introducing a new skincare product, especially one containing active ingredients, consider testing it on a small area first according to the product’s directions. Stop using the product if you develop significant irritation or an allergic reaction.

If you experience persistent or severe skin symptoms, seek advice from a dermatologist or other qualified healthcare professional.

If you want help putting these principles into a simple everyday routine, see our guide to a daily skincare routine for healthy, glowing skin.

Conclusion

Climate is one of several environmental factors that can influence how your skin looks and feels. Hot and humid conditions may leave the skin feeling sweaty or oily, while cold or dry weather can contribute to dryness and irritation. High-altitude environments can increase UV exposure, and urban air pollution may add another source of environmental stress.

Understanding how climate affects skin does not mean you need a completely different skincare routine for every type of weather. In many cases, a few simple adjustments are enough, such as choosing a suitable moisturiser, cleansing gently, protecting your skin from UV radiation, and avoiding products that cause unnecessary irritation.

Pay attention to how your skin responds as the seasons and environmental conditions change. If dryness, irritation, persistent breakouts, or other skin problems continue despite basic skincare, consider speaking with a dermatologist or another qualified healthcare professional.

A consistent routine that fits both your skin’s needs and your environment can help you maintain comfortable, healthy-looking skin throughout the year.

Frequently Asked Questions

Does hot and humid weather affect acne-prone skin?

Hot and humid conditions can make some people more prone to feeling oily or experiencing clogged pores. Sweat, sebum, sunscreen, and other products can accumulate on the skin, although acne itself has multiple causes. A gentle cleanser and lightweight, non-comedogenic products may be helpful if your skin is prone to breakouts.

Can a humidifier help dry skin?

A humidifier can be useful when indoor air is very dry because it adds moisture to the surrounding air. It may make dry skin feel more comfortable, particularly during winter or in very dry environments. However, it is not essential for everyone. If you use a humidifier, clean and maintain it regularly according to the manufacturer’s instructions.

Do I need sunscreen in winter?

Yes. UV radiation can still reach your skin during winter, even when temperatures are low. Sun protection is especially important during prolonged outdoor activities and in snowy or high-altitude environments, where reflected UV radiation can increase exposure. Use a broad-spectrum sunscreen with SPF 30 or higher on exposed skin and follow the product’s directions for reapplication.

How often should I exfoliate in different climates?

There is no single exfoliation schedule that works for everyone. Your skin type, sensitivity, the exfoliating ingredient, and the concentration of the product all matter. If your skin becomes dry or irritated in cold or dry weather, reducing exfoliation may help. Always follow the product’s instructions and avoid exfoliating irritated or damaged skin.

What is the most important skincare step in any climate?

Sun protection is one of the most important parts of a skincare routine when your skin is exposed to UV radiation. Broad-spectrum sunscreen, protective clothing, shade, and other sun-safety measures can help reduce UV exposure and its long-term effects. Beyond sun protection, maintaining a healthy skin barrier with gentle cleansing and appropriate moisturising is also important.

Disclaimer

This article is provided for general informational and educational purposes only and is not intended to replace professional medical advice, diagnosis, or treatment. Skincare needs can vary from person to person, and environmental factors may affect individuals differently. If you have a persistent, severe, or worsening skin condition, or if you are unsure about which skincare products are appropriate for you, consult a qualified dermatologist or healthcare professional. Always follow the instructions provided with skincare products and sunscreen.

References

1. American Academy of Dermatology (AAD) — Sunscreen FAQs
   Supports your claims about daily sunscreen, cloudy days, SPF, reapplication, and year-round UV exposure.
   American Academy of Dermatology — Sunscreen FAQs.
2. World Health Organization (WHO) — Ultraviolet Radiation
   Strong reference for your sections on UV radiation, altitude, clouds, snow reflection, and skin-cancer risk.
   WHO — Ultraviolet Radiation.
3. WHO — UV Radiation Questions & Answers
   Particularly useful for the specific statements about altitude increasing UV exposure, clouds not completely blocking UV, and snow reflecting UV.
   WHO — Ultraviolet Radiation: Questions and Answers.
4. PubMed — Climate and Skin Function: An Overview
   Excellent academic source supporting your overall discussion of temperature, humidity, altitude, UV radiation, pollution, skin barrier function, and premature skin aging.
   PubMed — Climate and Skin Function: An Overview.
5. PubMed Central — TEWL: Environment and Pollution — A Systematic Review
   This is especially valuable for your claims about transepidermal water loss (TEWL), climate, humidity, seasonal changes, and air pollution. The review found that pollution exposure was associated with increased TEWL, while climate/seasonal findings were more variable.
   PMC — TEWL: Environment and Pollution: A Systematic Review.
6. PubMed — Ambient Humidity and the Skin
   Useful for your humidity, dry-air, skin-barrier, and humidifier discussion. Importantly, the review also notes that the relationship between humidity and skin function is not completely straightforward, which fits the cautious wording you’ve used.
   PubMed — Ambient Humidity and the Skin.
7. PubMed — Variation in Skin Biology to Climate
   Supports your statements that temperature, humidity, and other climate variables can influence skin biology and TEWL.
   PubMed — Variation in Skin Biology to Climate in Shanghai, China.