You’re not supposed to wear white clothes after Labor Day, but hardly anybody knows why.
Laura Fitzpatrick relates multiple stories behind the bizarre rule in a piece for Time. One theory is that people wore white in the summer months to keep cool, but put it away customarily in the fall when the rain delivered mud (and stains). But this, she says, is far too logical a history for any fashion trend.
A more probable theory is that white was a symbolic color: those wealthy enough to "decamp from their city digs to warmer climes" did so, and they wore white on vacations to force contrast with the dark attire of urban life. So white garments represented leisure, and as a metaphor for summer they were stored in the closet when fall jobs and schooling began.
Some etiquette enthusiasts rebuff this tale. "There are always people who want to attribute everything in etiquette to snobbery," says Judith Martin, American journalist and authority on manners and style.