Staying Cool in 90-Degree Weather: What to Wear and Why

Staying Cool in 90-Degree Weather: What to Wear and Why

At some point this summer, most of us will likely be dealing with hot days with temps up to and well beyond 90 degrees. Even in our 8,000’ home base of Mammoth Lakes, California, we have more 90+ degree days every summer. Choosing the right clothes and following a few tips can keep you cooler this summer.

How Clothing Can Keep You Cool in Hot Weather

Knowing how to dress for hot weather is the first step in staying cool. Many people reach for light cottons, linen and synthetic fabrics for warm days. Merino wool doesn’t cross their minds since it’s often promoted as a fabric that keeps you warm. But natural fabrics Merino wool and Tencel actually make great summer clothing thanks to their ability to breathe, wick moisture and resist odor.

Have you ever cooled down with a cold washcloth on your forehead? You can take advantage of that principle with cooling clothing for hot weather. When you sweat wearing naturally cooling clothes, these fabrics take on the moisture and use it to keep cooling you. No one likes being sweaty in cotton clothes, but not all fabrics are created equal.

Choose Good Fabrics for Hot Weather: Merino Wool and Tencel

The Women's Natural Tank is made with naturally cooling Tencel.

Tencel, a fabric made from the pulp of sustainably sourced wood, is a game-changer for hot, humid weather. Tencel absorbs and holds onto sweat, which creates a unique cooling effect.

When Tencel absorbs sweat from your skin, the moisture stays within the fibers. As that moisture slowly evaporates in response to your body heat, it naturally lowers the temperature of the fabric and your skin. This process is known as evaporative cooling, and it helps you maintain a comfortable body temperature by mimicking the body’s natural cooling mechanism: sweat.

By holding more moisture than Merino wool, Tencel provides a sustained, long lasting cooling effect, making it an ideal choice for extreme hot weather clothing. Tencel is also extremely soft, so when you’re sweating you don’t need to worry about additional irritation from seams or the fabric rubbing against your skin.

Merino wool is naturally moisture wicking, breathable, temperature-regulating and odor-resistant, so pairing cooling Tencel with breathable Merino wool creates cooling clothing that works well on the hottest days. Our Men’s Natural Merino Tencel Tee, Women’s Natural Merino Tencel Relaxed Tee and Women’s Natural Tencel Merino Wool Tank Top are what we wear in 90-degree weather.

Go for Light Colors and Loose Fits

A man wearing the Ridge Solstice Hoodie in a light gray color in Death Valley

The Solstice Sun Hoodie is a go-to for hot, sunny weather.

When choosing a hot weather outfit, go for light-colored clothing with a loose fit. Lighter colors reflect the sun’s rays away from you better than darker colors. Keep in mind, though, that lighter clothing (both lighter colors and thinner fabrics) tends to offer less sun protection than darker, heavier clothing.

UPF clothing is great for summer days to avoid sunburn, and many UPF garments (like our Solstice Sun Hoodie) are made with a looser fit to allow plenty of airflow to keep you cool. In hot, humid weather, good airflow is key.

Use Hats for Shade

A good baseball cap or a wide-brimmed hat that shades your face and neck can significantly cool you down on hot days.

Beyond Clothes: More Tips for Staying Cool in Hot, Humid Weather

Jumping in an alpine lake is the best way to cool off on hot summer days.

Get outside, up high and away from pavement

Our favorite way to cool down is to jump into the ocean, a backcountry lake or a cool river. There’s no better way to get that immediate cool down, but busy days don’t always allow for an escape like that.

Sometimes heat and humidity feel more bearable sitting in a shady, grassy park or going for a short walk on a dirt trail. Pavement holds and reflects heat, and nearby nature areas can be several degrees cooler.

Finding higher elevation places to work, walk the dog or grab a bite to eat provides some heat relief too.

Stay hydrated

Hydration is key year-round, but especially on 90+ degree summer days. When you’re well-hydrated, your body can efficiently produce sweat, which keeps your body temperature regulated. Being properly hydrated helps you maintain proper blood circulation, which allows your body to distribute heat away from your core to your skin where it can be released.

Keeping a reusable water bottle with you is the best way to make sure you stay hydrated. When we’re out on Eastern Sierra trails, we like the Katadyn BeFree water filter to quickly drink from streams and lakes we pass.

Eating hydrating snacks in the summer can keep you cool too – watermelon, cucumbers and strawberries are a delight to eat on hot days.

Don’t forget electrolytes when you’re sweating a lot. Electrolytes, such as sodium and potassium, help balance fluids in your body, preventing dehydration and muscle cramps. Our favorite electrolyte brands are Skratch Labs for general day to day use and Liquid IV for big days in the mountains.

Take advantage of cooler times of day

Early mornings and dusk become the best times of day in the peak heat of summer. Adjust your schedule to spend more time outside when it’s cool.

Use natural cooling in your home

To avoid cranking the AC up, cool your home as much as you can naturally. Use cross-ventilation with windows open across the room to allow breeze to flow through, especially at night and in the cool early mornings and evenings. Then close up the windows when it gets hot midday.

If you get a lot of sun through certain windows, consider setting up a shade cloth outside or keeping the blinds closed during the hottest parts of the day. It might be worth looking into window films that reduce the heat that comes through your windows too.

If you don’t have air conditioning, fans can be helpful, and you can create a DIY air conditioner by setting a bowl of ice in front of your fan. A quick cool shower before bed or during the day is a great way to quickly lower your body temperature.


Making the right choices will help you stay cool and comfortable this summer, even when facing 90-degree days and high humidity. By wearing the right clothing for hot weather, taking advantage of natural cooling and staying hydrated, you can enjoy your outdoor adventures and daily activities despite the heat.


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