How to get vitamin d naturally<br>Learn how the sun creates vitamin d. Sunlight is a form of radiation that has two forms, ultraviolet a (uva) and ultraviolet b (uvb) radiation. Your main source of vitamin d occurs when uvb radiation strikes your skin. When this happens, the first steps of vitamin d synthesis in your body is triggered.

Can we draw the following conclusion?
You can synthesize vitamin d on cloudy days.
It's impossible to say