Socially correct

One of the social norms here in the US is to "not wear white after Labor Day". [Labor day is typically regarded as the end of summer. However here is Wilmington is was hot until 18 October (which is about 5 weeks after Labor Day)] It seems like a strange convention to stop wearing a certain colour. It seems that here in the South that you shouldn't wear white shoes during fall/winter (excluding sneakers and bridal shoes). I guess it is about dressing for the season, with white being a cool colour for summer.