Being outside is great for our physical, emotional, and mental health. When you’re heading outdoors, it’s important to take steps to protect your skin from the sun.

It might be tempting to skip sun protection when you can’t see the sun through the clouds. But the sun’s ultraviolet (UV) radiation, while invisible, is still very powerful. UV radiation can still harm your skin on cloudy days, causing sunburn and skin damage that increases your risk of skin cancer.

That’s why it’s so important to seek shade often and use sun protection all year long.

Read on to find out why sunburns can happen on cloudy days, how to prevent sunburns, and what you need to prepare when heading outdoors.

The sun’s UV radiation is a type of natural energy source we can’t see. But we can feel the sun’s UV energy. This is why unprotected skin feels hot or warm during daylight hours when the sun is out.

The sun’s UV radiation is strongest and most damaging between 10 a.m. and 4 p.m. daylight saving time (9 a.m. to 3 p.m. standard time) when the Earth is most fully exposed to the sun.

UV radiation grows even more powerful and potentially damaging during the summer, as the Earth tilts on an angle toward the sun (during the winter it tilts away).

If you live near the equator, the sun’s UV radiation is strong all year round because this part of the Earth sticks out closest to the sun. People living, working, or recreating at high altitudes also experience strong sun exposure for similar reasons.

The sun’s UV radiation can be strengthened and do more damage when it hits reflective surfaces like water, cement, sand, and snow.

So, it’s especially important to ensure you have adequate sun protection when you’re in places or situations where you’ll encounter these sun-magnifying factors, such as when:

  • swimming
  • at the beach
  • walking down a cement sidewalk
  • shoveling or playing in snow

It’s true that clouds do block some UV light. But more than 90% of the sun’s UV radiation can still pass through clouds on lightly overcast days and cause sunburn.

Types of ultraviolet (UV) radiation

The sun is the biggest and only natural source of UV light to which we’re exposed. Artificial sources of UV light, like tanning beds, can also cause sunburns and are extremely dangerous.

It’s not just one type of UV light that the sun sends out, but three types. Each has different characteristics based on its energy level, or wavelength, and carries different risks for our health.

Ultraviolet A (UVA)

UVA has the highest wavelength. It travels through Earth’s protective ozone layer deep into our skin, causing tans and sunburns.

UVA rays can also cause genetic damage to the skin cells, significantly contributing to skin cancer risk.

While weaker than the other two kinds of UV light, UVA is sent out by the sun in fairly constant amounts throughout the year.

Ultraviolet B (UVB)

UVB has a medium wavelength. It enters the skin’s outermost layers and can also cause tans and sunburn.

The ozone layer absorbs some UVB before it reaches Earth. Its levels change throughout the day and also seasonally: UVB is strongest in late morning to midafternoon, and from spring to fall in temperate climates. But UVB rays can damage your skin all year round.

Ultraviolet C (UVC)

UVC has the shortest wavelength. The ozone layer absorbs it completely, so it does not pose much of a risk to human health.

Certain people have an increased risk of sunburn, even on an overcast day. If you have any of the following risk factors, take extra care to protect yourself from the sun’s rays:

  • have lighter skin or eyes
  • have been sunburned in the past
  • are taking medications that can increase sun sensitivity, such as antibiotics and birth control pills
  • use certain skin care products known to increase sunburn risk, like retinoids and benzoyl peroxide

A note on skin color

A large 2010 study involving Black people living in California found that of more than 2,000 adults, just 31% used some kind of sun protection regularly, and 63% never used sunscreen.

People with darker skin tones have higher levels of melanin in their skin than people with lighter skin tones. Melanin protects the skin from sun damage — but only to a point.

Research shows even people with darker skin containing higher levels of melanin are at risk of both sun damage and skin cancer.

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Everyone is at risk of sunburn, even on overcast days.

Symptoms of a sunburn may present differently based on your skin color and the severity of the sunburn. A sunburn usually presents its most intense symptoms 24 to 36 hours after sun exposure. It typically heals within a few days to a week.

Some of the most common symptoms of a mild to moderate sunburn include:

  • blisters
  • confusion, weakness, or faintness
  • chills
  • dry, itchy, or peeling skin
  • fever
  • pain
  • swelling

People with lighter skin tones almost always experience severe redness along with a sunburn.

Medical emergency

Severe sunburn, while less common, can have serious effects that need immediate medical attention.

Call 911 or local emergency services, or go to the nearest emergency room, if you have a sunburn and:

  • symptoms of dehydration, such as dizziness, lightheadedness, and extreme thirst
  • rapid or weak pulse
  • irregular heartbeat
  • trouble breathing or shallow breathing
  • clammy skin
  • dilated pupils
  • chest pain
  • nausea
  • confusion or anxiety
  • lose consciousness

It’s most beneficial to use multiple types of sun protection. There’s not one type that does it all.

On both sunny and cloudy days, try to take as many of the following sun-protection steps as possible:

  • Cover up your skin with clothing, and look for “ultraviolet protection factor” labels on the clothing you buy.
  • Wear sunglasses. UV exposure also increases the risk of serious eye diseases over time.
  • Apply broad-spectrum sunscreen (which blocks both UVA and UVB rays) with an SPF of at least 30 (and 50 for skin that burns more easily). Apply generously and reapply as directed on the label.
  • Spend time in the shade when outdoors, especially on days when there’s a high UV index rating. You can find out the day’s UV index on most weather channels, apps, and websites.
  • Wear a wide-brimmed hat, or a cap with a brim that covers your face.
  • Try to head outdoors when the sun is at its weakest, in the early morning and evening.

Sunburns may be temporary, but the skin damage they cause is permanent.

What kind of sunscreen should you apply on a cloudy day?

Apply the same sunscreen you’d use on a sunny day on cloudy days; that is, broad-spectrum sunscreens with SPF of at least 30.

Note that naturally derived “reef-safe” sunscreens are also better for our bodies and nature, as they do not contain the toxic chemicals oxybenzone and octinoxate.

Cover all your bare skin with sunscreen, including your hands, ears, and neck. Waterproof sunscreens are preferable for people who are physically active or may spend time in or near water.

How much sunscreen should you apply on a cloudy day?

It’s recommended that adults apply about 1 ounce of sunscreen per application to fully cover their body. That’s about as much sunscreen as would fit inside a shot glass.

Make sure you rub the sunscreen fully into your skin. It takes about 15 minutes for sunscreen to be absorbed into your skin, so it’s best to apply before you head outdoors.

Reapply your sunscreen every 2 hours that you’re in the sun.

Sun protection is necessary not just on sunny days, but every day — even cloudy ones.

The sun is a powerful source of ultraviolet radiation that can cause significant damage, including sunburns and increase the risk of skin cancer.

No matter your skin color, it’s important to protect your skin from UV radiation. Keep your skin safe on cloudy days and every day by getting into a good sun protection routine.