When you look at old time photographs from the 20s and 30s, the men are wearing full wool suits, hats and often long overcoats, and the women long dresses, even in very hot cities like Milan, Italy, or Jacksonville, or Atlanta. However nowadays, everyone is dressed in shorts and t-shirts, as you would be drenched in sweat wearing a wool suit. Was formal attire back then that indispensable, or are the photographs all taken in winter? Was the weather back then cooler? Was it normal to be sweaty all day?
How far back do you want to go?
/u/mimicofmodes (formerly chocolatepot) has addressed this directly and indirectly:
Mimicofmodes is very prolific, so there may be another relevant answer that I missed.
/u/colevintage previously answered Did early modern women's clothing in the West reflect different climates?
/u/kittydentures previously answered Why did Republican Romans dress so lightly, while medieval Italians wore seemingly a lot of clothes, while living in the same climate?