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Here in Alabama, "summertime" usually means temperatures in the 90s (at least) plus a heapin' helping of humidity. Even if you don't live in the Deep South, chances are it's getting pretty toasty outside where you live. But that doesn't mean you have to give up your outdoor workouts. Try these keep-cool tips from Michele Olson, PhD, professor of exercise science at Auburn University, in Montgomery, Ala.

  • Drink up. Guzzle 8 ounces of water at least 30 minutes before you head out, then another 4 ounces every 15 to 20 minutes during your workout.
  • Follow the 3 L's. Clothing-wise, go with lightweight, light-colored, and loose-fitting. And leave the cotton at home (unless you enjoy wearing the equivalent of a heavy wet rag); instead, don togs made with tech fabrics like Coolmax and Dri-Fit—they wick sweat to keep you cooler.
  • Protect yourself. It takes time for your skin to absorb sunscreen, so apply it at least 30 minutes pre-workout. (Cloudy? Slather it on anyway—damaging UV rays can still penetrate.) And don't forget your hat and sunglasses.
  • Head for the trees. Route-wise, shady beats sunny every time.
  • Ease up. When it's super-hot, you need to cut your body some slack. Keep to moderate intensity (save those vigorous sprints for the treadmill), trim 10 minutes or so off your workout time, and exercise in the morning (before the earth has absorbed the heat of the day).
  • Know when to stop. Taste one of those myriad beads of sweat as they dribble down your face. Super-salty? You're probably losing too much water and sodium—and that can lead to cramping or dehydration. Head back inside pronto. Ditto if you feel nauseated, weak, or dizzy during your workout.
  • Think gym. If both heat and humidity are higher than you're used to—especially if you're planning an afternoon workout—then OK, you do need to choose treadmill (or a great DVD) over pavement pounding. Here's why: The evaporation of your sweat is what keeps you from overheating, and in pea soup–like conditions, that can't happen. So bite the bullet, hop on the sidewalk to nowhere, and remember: There's always tomorrow.