SF's foggy summer days still bring UV risks
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In San Francisco, it's easy to forget you can sunburn when it's cloudy — and that you don't need to feel the sun's hot rays to get a sunburn.
Reality check: 80% of solar UV radiation can penetrate light cloud cover — and infrared heat is different from UV radiation (which you can't feel), according to the EPA.
Driving the news: In the summertime, UV rays are at their worst at high noon, with San Francisco averaging a 9.2 UV index on cloudless days from June through August.
- That's when it's especially important to limit time in the sun and cover up.
Why it matters: UV radiation causes sunburn and is a risk factor for skin cancer.
- A UV index of 6-7 is the "high" range, 8-10 is "very high," and 11 and up is "extreme," which can lead to unprotected skin and eyes burning within minutes.
- Remember that next time you're about to head out without lathering on some sunscreen!
Between the lines: Altitude, latitude, cloud cover, ozone level, time of day and seasons all factor into the UV index.
A simple way to estimate your UV exposure: Look at your shadow.
- If it's shorter than you are (around midday), UV levels are higher and more likely to cause sunburn.