I still "observe" Labor Day to a certain extent ... I made sure I wasn't still carrying my straw bag on Labor Day. I kind of do a bit of a season switchover then, though I still wear open-toed shoes after LD. I don't wear white-white except for t-shirts, so that doesn't affect me ...
A couple other people brought up Labor Day in the context of fashion with me this year, so I know it's common for people to still be thinking about it ... perhaps because this is a warm climate and the weather may not change, though the "season" does ...