South Florida heat and humidity hit new highs. Is it too dangerous to exercise outdoors?

Aug 4, 2022

Edith Thomas starts her day with a morning walk, just as the sun rises. But lately, the 80-year-old Boca resident has been rethinking her routine as temperatures force her to stop every few blocks and rest.

“It’s so crazy hot,” he said.

South Florida has been hotter and more humid than usual this summer, with local meteorologists repeatedly announcing that “the big news is the heat” as they show temperatures that “look like” exceed 100 degrees.

In a state with beautiful beaches and parks, Floridians like to run, hike, bike, and play outdoor sports. Plus, exercising outdoors has health benefits: It can help prevent depression and anxiety because sunlight naturally increases serotonin, a hormone that affects your willingness to do things. “It’s a natural mood lifter,” says John Stout, a Broward County fitness and lifestyle coach.

Exercise itself, even something as simple as walking at a slow pace, releases endorphins, another feel-good hormone that lifts your mood.
The trouble, however, is that heat exhaustion can come on quickly and quickly progress to heat stroke, a life-threatening condition that occurs when the body’s core temperature reaches 104 degrees. On soccer fields or training camps, anyone exercising outdoors this summer needs to be aware of the risks of reaching a point where the body can’t cool down.

An added danger in South Florida is its high humidity levels. When humidity is high, sweat does not evaporate as easily and the body struggles to cool down, making it prone to heat exhaustion and heat stroke.

“The humidity actually makes you sweat less, but it feels like more because the sweat can’t evaporate off the skin,” said Dr. Cory Harlow, an emergency physician at West Boca Medical Center who has treated patients from heat-related illnesses. “It’s dangerous because you’re not cooling effectively.”

Timing is everything

Local doctors say no one should exercise in the South Florida summer heat between 10 a.m. and 5 p.m.

“If you want to exercise after 10 am, don’t exercise outside,” Stout said. “Especially if you are over 50 years old. Some younger people, athletes in particular, can handle the heat, but when you’re older, safety is top of mind.”

Research shows that older adults can’t adjust to sudden changes in temperature as quickly as younger people and are the most vulnerable when the heat rises.

Dr. O’Neil Pyke, medical director of Jackson North, said that when the sun is at its strongest in the middle of the day, it’s much better to exercise indoors, such as using a treadmill or stationary bike, taking group fitness classes or even to swim.

Pyke recommends making a change for the summer, using it as an opportunity to explore something new. “There’s no way your body won’t be affected if you’re outside in the blazing sun. But the heat shouldn’t stop you from exercising at home.”

Free apps like Nike Training Club, MyFitness Pal, and Daily Yoga offer personalized workout routines you can do at home. And some people have started using household items like textbooks and soup cans as exercise equipment.

Michael Zourdos, professor and chair of the department of exercise science and health promotion at Florida Atlantic University in Boca Raton, said that even as a marathon runner, he changed his exercise schedule to 4:30 a.m. during the summer and reduced his speed. “I also don’t worry about my pace in the summer. I find that my heart rate in 80-degree heat and 90-percent humidity is higher than it is in January when it’s 60 degrees and low humidity. The heat definitely affects your performance.”

Prepare to do it right

Hydration is essential when exercising outdoors. Stout says that he should start drinking fluids before he works out, like two to three hours before. Recommend lemon water.

If you are going to exercise at night, you can increase your body’s hydration level by eating water-rich foods throughout the day, such as cucumbers and watermelons.

During exercise, Stout recommends against quenching your thirst by drinking water or Gatorade. “Just take a sip. Don’t drink too much because it can upset your stomach and cause cramps.”

You’ll want to hydrate initially with about two to three cups or about 20 ounces of water within two hours before the start of outdoor exercise, and then seven to 10 ounces of water for every 10 to 20 minutes of activity, Zourdos says in FAU.

“It’s very important to make sure you’re hydrated before exercising outside,” he said. “You can’t catch up after you start. That is a bad idea.

Know the warning signs

Stout, who teaches outdoor group classes in Central Park at Plantation, says that the second you feel dizzy, you should pause.

Here are some signs that you are experiencing heat exhaustion or heat stroke:

- nausea or vomiting
- High body temperature (103 degrees F or higher)
- Hot, red, dry, or clammy skin
- Fast and strong pulse
- Lightheadedness or fainting

Harlow at West Boca Medical Center said the warning signs may be increasing.

“It could start off with muscle cramping and weakness, and then you’re sweating becomes less efficient and you get heat cramping. That’s the beginning of a slope towards danger,” he said. “As your body gets more overloaded, it goes to heat exhaustion and you feel lethargic, confused and your overall ability to function gets degraded.”

The next stage is more dangerous, he said. “It progresses to heat stroke and organ system failure, where he will have significant vomiting and confusion. You can go from mild to severe quickly, within 20 to 30 minutes, depending on your level of exertion and the temperature around you.”

To prevent that progression, Harlow recommends having someone with you instead of exercising outdoors alone and letting them know if you have any warning signs.

Cut down intensity

Regardless of how often or how intensely you exercise outdoors the rest of the year, experts advise you to relax during the summer.

“If you normally run four to five miles, no problem, when it’s hot and humid, it might be better to cut back to two or three,” Harlow said.

FAU’s Zurdos said another option is to exercise more intensely indoors a few days a week and less intensely outdoors once a week. “It doesn’t have to be all or nothing.”

If you’re going out to exercise, feel overwhelmed by the heat and have doubts, don’t go out, he said. “If you exercise for your health, why risk your health?”