We have a mechanic down here who wears flip flops practically every day.   Anymore he mostly always works in his own shop, so no need for those uncomfortable work boots some places insist on for some reason.  We met him on the way to the santa train one winter...in his standard foot wear. 

See lots of old guys wearing two shirts and long pants in triple digit temps during the summer. 

I've never "got" why you see women obviously wearing three or more tops when it's plenty warm.