I wear long sleeve and long pants even when hustling on rooftops all day in the sweltering sun when it's 90+. You can afford to not be a pusillanimous to stand there for an hour.
I don't give a rats butt what people would wear to my funeral. As long as they are nice enough to attend screw what they wear. I've attended too many funerals where just a few people show up and its really sad.