While vacationing in Idaho and Montana last week (blissfully off the grid), I experienced something beautiful: altitude. At 6,260 feet Stanley, Idaho is a mile higher than my home in San Diego. The skies there were a brilliant blue. There was daylight well after 10 PM. The mornings were a chilly 35 degrees. And I got sunburned.
How can this be? Montana is over 1,000 miles north of San Diego. Shouldn’t the sun be stronger down here?
Several things determine the sun’s intensity. The closer to the equator you are, the more intense the sun’s rays. But also, the higher up you are, the more intense the sun’s rays. Your UV exposure increases by 10% for every 3,280 feet in altitude; at 6,000 to 8,000 feet in elevation, you’re exposed to 25% more ultraviolet radiation than at sea level.
Also, snow (which fell during our mid-June trip) is an efficient reflector of sunlight. When skiing or hiking in snow, 80-90% of UV light is reflected at you, dramatically increasing your sun exposure. Grass in comparison reflects only about 3% of sunlight.
Water, especially when still, also reflects sunlight. Still lakes, including the beautiful Yellowstone Lake pictured above, can reflect up to 100% of UV light (hence the term mirrored lake), doubling your UV exposure.
So although you might feel hot lying on the beach in June in Southern California, you might be more vulnerable to sunburn on a chilly hike in Yellowstone after a June snowstorm, which is exactly what happened to me. (Hence the Stetson later in the trip…)
Photos: Madsit, Stanley, ID (top) Purticortico Yellowstone Lake, WY (middle) Dermdoc White Bird, ID (bottom).
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8 Comments
Hi Dr. B, I’m so glad you posted this. I learned this the hard way hiking up a snow-capped volcano in New Zealand. I was burned even through the shaded goggles — the burn took a full month to shed and heal.
Wow! How high did you go? I’ve never been to New Zealand, but would love to. Are you from there?
Did you get burned on your scalp?
@Dr. Benabio I’m not from New Zealand, but a word of warning — the sun there is absolutely intense. It’s probably due to the gaping hole in the Ozone layer.
I could’ve told you that. My brothers got snow blindness years ago when we were all young while skiing. I can still see them and their friend Landon screaming and crying as dad brought them into the house, their eyes bandaged up. Apparently it was seriously painful.
And being dragged kicking and screaming camping more then once in my life I’ve gotten many sunburns while fishing. I’m sure I’ll one day get skin cancer because of all my exposure as a kid. If not, I’ll probably bruise easily like my mom. Her hands are always black and blue with multiple places where she bleeds. And the doctor says it’s because she was in the sun too much as a kid.
Is it possible to have developed an extreme sensitivity to the sun’s radiation after having been badly sunburned on numerous occasions as a child and teenager? I feel almost allergic to it now.
Thanks for the article. I really like it. According to my idea on the mountain we are more likely to sunburn.
Hey doc, are your sure your numbers are correct? According to a high altitude MD that I am friends with, it’s 6-8 percent for ever thousand feet above sea level. Much worse. Not only is a great sunscreen essential but also great eye protection, sunglasses that are large are best. Take a look at any athletes here in the high country, and most of them, sadly, look far older than their real ages due to sun exposure.
Cheers, and thanks for spreading the word.
Savory Tv
Resident of both Telluride and Aspen CO
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