With heat indexes above 100... doctors encourage you to stay inside to avoid suffering heat exhaustion. First, doctors say use common sense when doing anything outdoors. Especially exercise... between 10-am and 3-pm is the hottest. If you do have to exert yourself outside... maybe you work in the heat... Take breaks every half hour. Of course, children are especially succepital... don't leave them in a hot car. And check frequently on your elderly friends and relatives as well. Finally... you've heard it before... drink plenty of fluids...and if you find yourself feeling light headed or dizzy... go inside immediately.