Heat of the summer? That's when I put the mountain bike away and ride the road bike. 15-20 mph breeze sure beats 5-8 mph breeze. Plus there is not a breeze at all in the woods(here).
What is hot there? Here, the term hot isn't used until it's over 95 . We start a lot of our road rides in the evening over 95 degrees. Seemed like all last summer it was about 97 when we started our rides out.