Working out in the summer heat is tough. Not only is it already 100 degrees out, but your body is heating up because of the workout you're giving it. To counter overheating, The New York Times shares a few ways to cool yourself down, including precooling, and evidence that the irresistible urge to dump water on your head really works.
Before you start exercising, you can use a couple precooling techniques to keep your temperature down. This includes drinking a slushie, or even just draping a cold rag around your neck. These precooling techniques can improve endurance in hot weather exercise by nearly 4 percent.
But only when cold water was poured over their heads did the volunteers report feeling blessedly cooler than in the other exercise session. They also said that the workout felt noticeably easier, and their skin temperatures were lower than in other sessions.
That said, dumping water on your head doesn't improve performance. It simply makes the heat more tolerable so you actually finish your workout. Just remember to actually drink a bit of that water too.