Dear Tom,
Whenever we have an exceptionally hot day, I often hear people say, “Be sure to put on extra sunscreen since it’s so hot!” I thought that it’s the UV index that determines the intensity of the sun’s rays, not the temperature or humidity. Wouldn’t a sunny, 70-degree day in July pose the same threat to your skin as a sunny, 90-degree day?
— Kathy Stein
Dear Kathy,
“For the most part, you are correct,” says Dr. Bryan Schultz, who prepares the sunburn times that we give on this page. “Given the same clear sky, the sun’s angle of elevation determines most of the intensity. This will be higher the closer you are to solar noon, the summer solstice and the equator. Some studies have shown a slightly greater burn potential for skin with higher heat and humidity, so there is a small adjustment in our sunburn times with heat indices over 100 degrees.”
