I completely agree. Paying attention to your dog and conditions when it is warm is imperative. Wasn't it only a few years back that guys were literally running their dogs to death in South Dakota because of the heat during the early part of the hunting season?
My dog doesn't seem to start hitting her stride until it gets in the 40's too. I've run her in sub-zero temps, but with a coat/skit plate on to trap some body heat. We can get extremely cold here and that can be just as bad.