I live in one of the sunniest places as well, I am a white female, I too have tested very low Vit D.
Concerned about an article I read that suggests too much Vit D is harmful.
I don't know how old you are but as we get older we become less efficient at getting vitamin d from the sun. For example at my age 61 I'd have to stay in the sun 1 1/2 hours and then I might not get enough.
THe amount of vitamin D supplementation that you should take to resolve deficiency is open to debate. I had problems tolerating mega-doses (50,000 IU D2 twice weekly). However, I'm doing well on 4000 IUs daily which my endocrinologist tells me is the maximum dose I should take for long term supplementation. Now, if your vitamin D levels get over 100 (I believe that's the level) you could develop vitamin D toxicity but as someone on this forum said that's only a problem for young lifeguards. Read the articles by Dr Holick that Bisan recommends.
Dr. Mercola also has many articles about vitamin D and vitamin D deficiency. He stated much the same as what Bisan said in the beginning of the thread. Washing immediately after sun exposure does indeed remove the protective outer layer that is needed because we still synthesize the sun in our skin well after coming inside out of the sun. There really is such a thing as too clean. While we don't want to go back to the dark ages when people needed to bathe more often, our culture does actually bathe too much. There are other reasons for not bathing as often as is ingrained in our culture, but primary to this discussion is the need to leave that protective layer of protection in order to help with vitamin D synthesizing in the skin. You don't have to not bathe, because no one wants anyone to do that, but bathing too much in this case is really not a good idea.
Can only get D3 from sun if sun is above 50•
in the sky. US Naval Azimuth chart.
If cloudy outside you won't get UVB rays. Most of the US has no UVB rays from October to mid March. The links below show you when UVB rays are available in your area.
Video on how to use the chart:
The URL for the US Naval Observatory Azimuth table is http://aa.usno.navy.mil/data/docs/AltAz.php