Well it was the clever Romans that postulated about this temperature peak by weaving tales into the sky. Evaporation carries away large amounts of heat, cooling you down. Often it s not just the heat your body is battling, it s the humidity as well.
Humidity is a measure of the amount of moisture in the atmosphere.
Physical activity more tiring than usual. Heat cramps and heat exhaustion possible with exposure. Heatstroke possible with prolonged exposure. See article Weather and Your Health for more on heath ailments. Take a trip to the hottest location in the United States.