Members of the National Association of Athletics' Trainers say exercising during cooler portions of the day in the early morning or late evening can help avoid heat illness.

Back off on exercise intensity or duration if not feeling well. On the other hand, rest breaks are an important defense against heat illness, and proper sleep habits decrease risk as well.

"We're hoping to educate athletes, coaches, parents and healthcare providers about what can be done to prevent and treat heat illnesses," athletic trainer Brendon McDermott of the University of Connecticut said in a statement.

NATA recommends gradually increasing activity in terms of intensity and duration in the heat. This prepares the body for more intense, longer duration exercise in warm conditions, and helps prevent injury and heat illness.

Hydrate properly before beginning outdoor activities and drink water or sports drinks throughout, McDermott says. Darker urine color is a quick indicator of dehydration -- the color should look more like lemonade than apple juice.