MARIETTA, GA. -- When it gets hot in Georgia, normal Southerners buy a watermelon, make some real lemonade (a third of a lemon per glass of water), and turn the sprinkler on the lawn chairs.

We don't quit exercising, though; we just do it smarter. Here's how. And don't think you're too smart to need these tips: That's what all those sporty-looking folks in the emergency rooms thought.

Read carefully, share with the family (including the kids), and proceed:

Think ahead and think water. Don't trust your senses to tell you if you need agua. "The body," says Arno Jensen of the Cooper Clinic in Dallas, "doesn't do a good job of warning us about its water requirements."

Even if you're not thirsty drink a glass or two of cool water about an hour to 30 minutes before you exert yourself -- take a long walk, for instance. Then drink another cool or cold glass just before you head out. Studies show the coolness itself helps your thirsty blood and cells suck up the water.

When your body's low in water, blood actually thickens and cells can lose their "homeostasis" or equilibrium. And you, a wise exerciser, don't want unbalanced cells or sludgy blood: Deliriums, heat strokes, heart attacks, cramps, perhaps the heartbreak of psoriasis hold hands with those two bad guys.

How do you know if you're taking in enough water? "Weigh yourself before and after exercise," Jensen says. "If you're exercising moderately under six miles, you shouldn't lose more than a pound or two."

"If you're vigorously exercising for more than six miles, you shouldn't lose more than four or five pounds. And weigh yourself on several different days," says Jensen. "If your weight loss is excessive, you're not drinking enough water."

What about water along the way? A little water every 20 minutes is the best plan. Even if you're just pleasure-walking for more than 30 minutes, you should take along a pint of water for every hour you walk. Plastic canteens are inexpensive.

What about drinking soft drinks, juices or specialized "replenishment" supplements? Save your money. Any drinks with sugar (even natural sugar such as that in a juice) can slow you down; carbonated drinks cause stomach distress; caffeine dehydrates you; exotic fluids may work to some degree, but probably not better than water.

Choose your clothes carefully. A broad-brimmed hat helps a lot. I jog with a Greta Garbo-type fedora, and the neighbors who see me probably lose more weight laughing than I do jogging, but that's okay. I'm cool anyway.

Wear loose-fitting, preferably cotton, clothes, too. The right clothes wick moisture away from the body and cool you as your sweat evaporates.

Never wear clothes that won't let your body "breathe." Nonporous materials, particularly in this hot weather, can kill you.

Pick your surface and your route. If you plan to exercise on black asphalt, why not save time and exercise instead in your wok? And where can you find some shade? Temperatures effectively drop 20 degrees when you move out of the direct sun.

And here's the best tip passed on by Arno Jensen: "In the summer, exercise with the wind going out and against the wind coming back." Your body needs the cooling, evaporating breezes much more on the return.

Start slow and stay slow. Heat and humidity actually make your body work harder to achieve the same benefit. If you're used to running a 10-minute mile in cool weather (about my pace unless I'm being chased), run a 12-minute mile now and you'll accomplish the same amount of work. And if you have any health problems -- including too much weight -- slow down even more and exercise a little less.

Cool down gradually. If your heart goes from frenzy to lazy instantly, particularly in hot weather, your blood pools and you could go boom, pass out in a flash. Walk slowly until your pulse is back to normal and your body feels relatively cool.

Ideas for Plan B, when it's just too hot:

Switch to indoor exercises. Rather than running or biking, why not spend the month speed walking in a mall? Leave credit cards at home.

If you're close to a pool, start exercising in the pool. Walking fast back and forth across the shallow end will wear you out (and work more muscles) than a jog any day. For a real workout, walk in neck-deep water and play whirlies with your hands for 15 minutes.

Know the danger signals and take appropriate action:

First-stage heat problems: Heat cramps and simple muscle spasms usually happen first. If you feel a cramp coming on or begin to lose your normal mobility either in your legs or your hands, stop exercising immediately, seek shade and drink cool water. If absolutely no water is available, drink other, sugarless, liquids). If you're careful, you can try exercising again later in the day.

Second-stage heat problems: Heat exhaustion. You begin to sweat profusely and probably have a headache or dizziness. Heat exhaustion can very quickly become life-threatening. If you experience even ONE of these symptoms, stop exercising immediately, lie down, and drink water. Do not under any circumstance exercise any more this day, and drink extra water for the next 24 hours.

Terminal heat problems: A heat stroke. You can die very quickly when this happens, but you won't worry about that. At this stage, you're unaware of the symptoms: Sweating completely shuts down and the skin becomes dry and hot; you become dazed, confused, disoriented and pass out. Life can end in minutes.

If you see a fellow exerciser with these symptoms, quickly try to cool him or her with ice packs or cold towels. Be creative: Make compresses from clothes soaked with soft drinks, if need be, and call an ambulance quickly. Cooling the body is critical.

If no other cooling methods are available, place the victim in an air-conditioned vehicle until help can arrive.

All this may be enough to make you plan a hot and heavy summer of canasta, but don't give in to that temptation. Post these tips on the fridge, find your water bottle and floppy fedora and join me for a little-slower workout.