Staying hydrated is critical if you're physically active in hot weather.
But individuals have different hydration needs, so you need to assess your personal sweat rate, according to Brendon McDermott at the University of Tennessee at Chattanooga.
"Sweat rate is very simple to calculate: weigh yourself before exercise, with as little clothing as possible; exercise for half an hour and don't drink or use the bathroom for that half hour; weigh yourself again, wearing the same amount of clothing to see how much you've lost," he explained in a university news release.
If you've lost a pound, for example, that translates to about 16 ounces of fluid that you'll need to replace. Sports organizations suggest dividing your total by four to see how much water you need to drink every fifteen minutes while exercising to replace your lost fluids.