I can’t handle the 90-deg hot, humid heat in the sun. When I’m sweating so much I can’t get enough water and electrolytes back in me, I’m done. Several times I’ve taken off early before sunrise to beat the afternoon heat. I want to be done before that afternoon sun bakes me.
Although I enjoy the summer bicycling more, cold doesn’t actually bother me too much when dressed properly. The winter has other problems like snow, ice and lack of daylight that will keep me from cycling as much.