Wow, that says something for my fashion knowledge... Right? I hope not!
This comes back to the "Who tells you what to wear?" question.
Looking at this historically, people often wore white during the summer months to keep them cool, or to tell their status in society (poor people could not afford white clothes). Then in the fall months they changed back into darker colors to keep the appearance of mud and dirt low.
Well that does make sense, but now a days, most people will still wear white after labor day (including myself), because we have advanced laundering techniques.
I have to say that this is one of the fashion rules that I will break constantly, and if I loose my status as a fashionable individual... so be it. ;-)