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You're probably well aware that excessive sun exposure is associated with health risks, whether it's something as simple as a sunburn or more serious issues such as skin cancer. And while you likely take care to wear sunscreen and protective clothing when the sun's bright and the weather's hot, you may not take the same precautions -- if any -- when it's cloudy.
Can you get a sunburn on a cloudy day? As it turns out, you can. Let's examine how that's possible and what you can do to prevent it.
Types of Ultraviolet Light
The sun emits three types of ultraviolet rays: UVA, UVB, and UVC. The Skin Cancer Foundation describes the key differences -- the types we generally have to worry about are UVA and UVB, as UVC rays typically don't reach the earth because the atmosphere absorbs them.
The predominant type of ray is UVA, which accounts for 95 percent of the ultraviolet radiation that reaches the earth's surface. UVA is the primary contributor to skin aging, wrinkling, and skin cancer, while UVB rays cause skin reddening and sunburn.
The intensity of sunburn-producing ultraviolet radiation at a particular time and place is measured by the UV Index, which ranges from 0 to 11. Zero means there's no UV radiation -- this typically occurs only at nighttime. A UV Index score of 10 generally corresponds to midday summer sunlight with a clear sky, and a score of 11 means extreme risk of harm from unprotected sun exposure.
So can you get a sunburn on a cloudy day? Although it's less likely than when you're out in full sunshine, it's possible.
While clouds do reduce some of the sun's UV rays, they don't block all of them, as the Skin Cancer Foundation explains. UVA rays can penetrate clouds, and they can also reach below the water's surface. UVB rays can also damage your skin year-round, cloudy or not, especially at high altitudes where there's less atmosphere to absorb ultraviolet radiation. Reflective surfaces like snow and ice also intensify UVB rays and their effects on the skin.
What can you do to keep your skin safe in conditions that you might not have thought posed a sunburn threat? Here are a few tips:
- Apply sunscreen on cloudy summer days when you plan to be outside for long periods of time, especially if you're hiking or at elevation.
- Check the UV Index before you head out on your outdoor activities. This will give you a sense of how much you need to protect against excess sun exposure and what SPF sunblock to use.
- On cooler cloudy days, wear long sleeves and pants to cover as much skin as you can, and pack sunscreen in case it warms up and you need to take off a layer.
- Use water-resistant sunscreen while you're swimming in the ocean or a pool to block those water-penetrating UVA rays. Be sure to reapply once you're out on dry land.
If you're outside on a cloudy day, remember that the sun's rays are still hitting you. You may not have to go to the same lengths on a hike under cloud cover as you would on a hot, sunny day at the beach, but you can still take precautions to prevent burning and keep your skin healthy for the long haul.