I remember when I was in the UK in summer 2000 and I was staying with my cousin. It was a lovely sunny 30°C one day and he came home from work, flaked out on the couch and said "It's so hot"!
I said "this is great, where's your push bike?"
35° is getting "hot". 38° is "stop playing outside". 40°+ is "go find some air conditioning"