Shelties in the heat?

I am curious about shelties and maybe getting one in the distant future. But I live in Alabama so I'm wondering if it would be cruel and unusual to have a high energy dog with a double coat in the heat. I do have a Pomeranian, so he has a double coat, but he has little legs and less energy I am guessing. I plan to do walks early in the morning or at night but would that work with a sheltie?