The old cliche is true: It’s not the heat, it’s the humidity. Staying safe while doing strenuous activity in Florida’s August takes some knowledge. We talked to Patrick Mularoni, the medical director of sports medicine for Johns Hopkins All Children’s Hospital, about the roofers, beach bar singers, pizza bakers and glass artists who work in hot jobs.RELATED: These are Tampa Bay’s hottest jobs — literallyWhen you get too hot, your body tries to lower your temperature by releasing sweat, which causes a cooling effect when it evaporates off the skin. That evaporation is the key to keeping cool. “The higher the humidity is, the more difficult it is for the water to evaporate off your body,” Mularoni said. In a drier climate, it evaporates quickly.Adults who work outside in steamy Florida can learn from student athletes. Mularoni coaches youth sports teams and he tells his players their urine should be almost clear by the time they go to bed at night. That tells them they’ve been drinking enough water. “If it’s the color of apple juice or darker, you need to drink more water because you are becoming dehydrated,” Mularoni said.And some people are “salty sweaters,” he said, meaning they have more salt in their perspiration and should add sports drinks with electrolytes into the mix. Look for white rings on the sweat stains of T-shirts or hat rims. If you’re a salty sweater, drink one sports drink about an hour into a sweaty session, in addition to the water you should be gulping every 15 minutes. Hydration has come to the forefront of concern in medicine, Mularoni said, and it is one of the staples of pre-season training. He tells athletes to drink 16 ounces of water at least an hour before training so they start off adequately hydrated. Then take two gulps of water every 15 minutes, about four ounces. Your goal should be to drink before you are thirsty. Coaches also spend time getting athletes “climatized” to our intense heat, especially football players. They don’t practice in full helmet and pads until they’ve trained for at least a week in the heat. That’s why he isn’t surprised that people like roofers and pizza bakers can keep at it year after year. They’ve been climatized. Adults often add alcohol or caffeine to the mix, both of which can make you dehydrated because they increase urine output. If you are drinking them, you need to up your water intake as well, he said.He has noticed that people who work outside, such as commercial fishermen, tend to choose salty foods, probably because their body is craving the electrolytes they lose from sweating. “Most people who work outside become good about that. They learn to not only drink appropriately but eat appropriately,” Mularoni said. “I’m not saying I recommend eating salty foods. But people who work outside a long time tend to eat saltier foods and drink more water.” Contact Sharon Kennedy Wynne at email@example.com. Follow @SharonKWn.