For those athletes who cannot endure training at 100 degree temperature, I feel your pain. Sweat is pouring all over your body 5 minutes after the start of a warm up. You're thirsty. Halfway through your work out, your body aches as fatigue sets in. Then, you want to give up after a grueling exercise.
That's the life of an athlete living in Central California during the summer months. Trust me, I go through this scenario every year. It is something that my body endures at heat extremities. And I HATE IT!!
I envy people who live in places where the weather is consistent every year such as San Francisco, Virginia Beach, and Seattle. If you want to add Denver to that list, minus the snow, you may do so. SF, VA Beach, and Seattle are very weather-training friendly. They are not too cold, or too hot. Just right...
In the meantime, I must make the best of the Mediterranean climate that Central California offers. Plus, CenCal has great bike and run paths for everybody to train. Without them, I don't know what I would do for an outdoor activity.