MANKATO, Minn. — The heat is on, especially across the South, Southeast and portions of the plains. The National Weather Service has issued several heat and excessive heat advisories.

When summer goes from warm to hot, exercising could become risky — unless you’re prepared. “Staying active, even exercising in hot weather, can be done safely, but you really have to pay attention to the environment and your body to make sure a good thing doesn’t go bad,” says Chaun Cox, M.D.

, a Mayo Clinic Health System Family Medicine physician and an avid runner. Here are a few tips from Dr. Cox for exercising in the heat.

___ If you haven’t been exercising in hot weather already this summer, don’t choose a hot day to start. Your body needs to acclimate to the heat, so start with shorter periods of exercise and gradually extend the duration of your workout. High humidity prevents sweat from readily evaporating from this skin, which puts added stress on your body.

And pay attention to the forecast — and the sky. Severe weather can develop rather quickly, and there are no extra points for trying to outrun a thunderstorm or tornado. ___ Your body cools itself by sweating, and if you stay hydrated, the body is pretty good at cooling itself.

When you become dehydrated, your body starts to store heat inside. Your core temperature begins to increase, and that can put your organs and nervous system at risk. Drink water before, during and after you exercise.

Additionally, make sure .