If the humidity is high, I wait till late evening to ride. Like around 7 or 8 pm. And with the heat, probably around mid 90's, but even then, I don't ride in mid day with the sun directly on top. To avoid the most harmful sun rays, wait till your shadow is taller than you are. Don't be in the sun when your shadow is shorter than your height.
Opportunity is missed by most people because it is dressed in overalls and looks like work. ~Thomas Edison