When can I stop walking at dawn and walk at a normal hour?

Heat. I was told to walk early and I do, in Papago Park, before the sun gets going. Habit. By the time I leave, the car park already has a few cars, all belonging to people who look like they have done this for years. Gap. Nobody told me when the early start stops being necessary. Now that the winter visitors are starting to arrive, when do the mornings in Phoenix get comfortable enough to walk at a normal hour?