Pat Shingleton for Friday, Aug. 9, 2013

Today’s showers and thunderstorms may help in lowering the expected daytime high by 17 degrees. This will occur only if the showers last longer than 20 minutes. High humidity makes the body work harder to cool itself by its own evaporation cooler, better known as sweat.

One of the first signs of dehydration is an elevated body temperature and no sweat. When wind and cold affect the body during the winter months, the wind chill values are calculated.

During the summer, it’s the heat index or the apparent temperature. Sunstroke, heat cramps and heat exhaustion occur when the index tops 104 degrees.

Five years ago, deodorant maker Old Spice named Phoenix as the sweatiest city in America; Las Vegas; No. 2, Tallahassee, No. 3; and Baton Rouge, No. 9. Fastcast: Showers.