For me, temperature tolerance is completely dependent on humidity levels. I can deal with high-80Fs and even low 90Fs if the humidity is low. But if it's the least bit steamy, even upper 70Fs can be miserable. Same with winter. And of course, what's uncomfortable at the start of a season can feel just fine by the end, after I've acclimated. 15F in December means you dress in 47 layers of down and wool, but 15F by mid-January means dashing from the car to the store without bothering with a coat.