I figured out for my Lat and Long (San Diego) that 15 minutes of shirtless sun per day is generally enough, in the summertime I got it . What about wintertime? Any educated guesses in order to obtain decent level of 25 hydroxy blood levels?
asked byCory151 (1677)
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on January 18, 2012
at 10:26 PM
My UVB measurements in the DC area showed that about 1/4 the amount of UVB rays reaches the ground at solar noon on the winter solstice vs. the summer solstice. In San Diego I'd expect the difference to be lower -- perhaps between 1/3 and 1/2. Worst case maximum sun angle (solar noon, winter solstice) in San Diego is 34 degrees. In DC we have 34 degrees in mid-November, at which point my measurements showed 46% UVB output relative to the summer solstice.
There are other factors which can make things more complicated (e.g., how standing up vs. laying down and the sun's angle can influence how much UVB your skin sees) but this gives a decent approximation.
on January 19, 2012
at 03:02 PM
Been laying out whenever the opportunity has presented itself. San Diego is so bizarre I tell you. One day it's 78 and beautiful clear blue skies, and the next it's low 60s and cloudy and foggy and cold. But the winter sun of San Diego definitely allows you to stay under it longer without burning at all. I always limited to 12-15 minutes per side (so no more than 25-30 minutes total exposure) during the summer. But just 2 weeks ago I was staying out for at least 20 minutes per side and barely felt like I layed out. I don't have any technical number details like Kilton... just my personal experience :)