like thegrouse, I've harvested some nice bucks in hot conditions. One was in 115 degree weather. They simply do not want to leave their beds, so they are very vulnerable.
Sure you can kill game in hot weather. But it'smuch more fun when cold. Plus it's a pain getting an animal gutted, skined and in the cooler. Had one spoil on me twenty minutes from the house. Like beer I like mine frosty.