Frank, the first time we went to the States, think I was 18 and of course we had no internet to check things then, we called John's aunty to see what the temperatures were like and according to her Summer was over and it was cold, they'd started wearing jumpers. They're right on the US/Canadian border, and we knew that it gets cold up north in Winter so off we went in September with jumpers and Winter coats in our cases.
It was mid-20s.
I had to be taken to a mall on the first day to buy shorts and t shirts...