Why hot weather makes you tired and how to stay energized
ST. LOUIS — The summertime heat is just around the corner. When you’re outside in the heat, whether it’s for a few minutes or maybe an hour or so, it can really zap your energy. Why does the heat make us so tired?”
Two words: heat index.
What a lot of people tend to notice in the middle of June, July, and August is that the heat can wear you out and make you crave an afternoon nap.
“Your body is working harder than it normally does,” Dr. Jamil Neme, a sports medicine physician and assistant professor at Saint Louis University’s School of Medicine, said. “You can get fatigued more easily, and if you’re not hydrated well enough, that’s another reason you start to get more fatigued.”
Your body kicks into overdrive to keep you cool, your blood vessels dilate, and the sweating begins.
“You have blood vessel changes where they get wider, vasodilate, and that attempts to have the body cool off,” Neme said. “And, also, you start sweating more. And when the sweat evaporates off the skin, it’s a cooling mechanism that we have for our body.”
But when the humidity is high, the evaporation of sweat off your skin becomes more difficult. The sweat cannot effectively evaporate and cool you like it would on days with low humidity. This can lead to dangerous heat-related illnesses.
“Heat exhaustion—you start having signs of more sweating. Your heart rate increases, headaches, nausea, and we’re worried about dehydration at that point,” Neme said. “We’re worried about heat stroke when people have those same symptoms but then also having confusion, so that’s why they call it a stroke, because you have a stroke-like confusion state, and that’s a medical emergency.”
Proper hydration is crucial in the summer to avoid heat-related illnesses. Doctors say women need roughly nine cups of water a day for full hydration, whereas men need about 11 cups a day. But keep in mind that you will need more during strenuous outdoor activity during the summer.
Not only is the heat and humidity combo making you feel fatigued, but being in direct sunlight can have that same effect.
“If you do get a sunburn, your body has to work harder to heal that,” Neme said. “It has an increased metabolic rate to repair that damaged skin, and you also need more hydration to do that process, so it’s definitely important to have sunscreen and do everything you can to avoid those.”
The tiredness that comes with hot weather has a tendency to sneak up on you without even realizing it.
“If you’ve gotten to the point where you are feeling tired and thirsty, it’s definitely a good time to go inside, find some air conditioning if you can, get some shade, and then definitely put in some hydration because it’s probably not going to get any better if you’re staying out there,” Neme said.
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