I ride from the 50's up to about 110F. Here in New Mexico **** gets real after June 1st, especially in the afternoon - but as they say "It's a dry heat" and I don't know, I just somehow got used to it. There is a sort of point around 100F where if I stop for more than a few minutes, it's very rough to get going again, so no afternoon-long rides in the summer.
I used to love the cold - I'm an old ice climber from pre-climate-change New England. I lost some toenails due to frostbite, and did some bigger climbs in the Andes that weren't exactly warm. Then I got old, and while I still love a day on the slopes at Taos, I'll be god damned if I'll ride a bike in the cold any more.
Never thought I'd shrug at putting 50 miles in at 101F, but 7% humidity and lots of water help.
I guess things change.