# To what extent do clouds affect suntan/burn time or intensity? **URL:** \ **Category:** Factual Questions\ **Created:** [April 20, 2006, 10:29pm UTC](https://boards.straightdope.com/t/to-what-extent-do-clouds-affect-suntan-burn-time-or-intensity/353536 "2006-04-20T22:29:07Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![CC](https://avatars.discourse-cdn.com/v4/letter/c/f1d935/32.png) [@CC](https://boards.straightdope.com/u/CC)\ **Post date:** [April 20, 2006, 10:29pm UTC](https://boards.straightdope.com/t/to-what-extent-do-clouds-affect-suntan-burn-time-or-intensity/353536/1 "2006-04-20T22:29:07Z")
Yep, that’s pretty much it. I presume that thick cloud layers would pretty much block the UV and thin layers would do pretty much zip zilch nada. Is there some sort of rule of thumb that could be used? I’ve never really noticed enough to be able to have my own internal law. Having just come off a week on the beach, I still couldn’t tell if I was more or less susceptible to rayburn when the sun went behind the clouds. Anyone have the real straight dope? xo, C. ---
**Author:** ![Doctor\_Who](https://avatars.discourse-cdn.com/v4/letter/d/ed8c4c/32.png) [@Doctor\_Who](https://boards.straightdope.com/u/Doctor_Who)\ **Post date:** [April 20, 2006, 10:34pm UTC](https://boards.straightdope.com/t/to-what-extent-do-clouds-affect-suntan-burn-time-or-intensity/353536/2 "2006-04-20T22:34:34Z")
Here’s some guidance from the [FDA:](http://www.fda.gov/fdac/features/596_7sun.html) > [@](#): > > Don’t be fooled by cloudy skies. Clouds block only as much as 20 percent of UV radiation. UV radiation also can pass through water, so don’t assume you’re safe from UV radiation if you’re in the water and feeling cool. Also, be especially careful on the beach and in the snow because sand and snow reflect sunlight and increase the amount of UV radiation you receive. The Doctor