You know it's hot when even the ADV guys are squiding in T-shirts. I did the same last night, but I'm just around the corner from BB. This afternoon I went to the US side of Niagara Falls wearing leather pants and a mesh jacket, and I was fine. There was an hour wait at the border, but luckily I was at the Rainbow Bridge and there was a decent breeze. I debated removing my jacket, but figured it was keeping the sun off my skin and probably keeping me cooler than without.
Long and short, cherish the days you can ride because the season is so short. Doesn't the saying go "I'd rather sweat than freeze"?