Heat can be dangerous, but health experts say there are ways to manage the threat.
Scorching temperatures, especially combined with high humidity, pose risks particularly for children, older people and those with certain health conditions. Anyone can suffer from heat-related illness.
Climate change is also exacerbating heat waves and heat stress.
When heat becomes dangerous
Dangers posed by hot weather depend on more than the temperature. The most detailed measurement is called the wet bulb globe temperature (WBGT), which includes temperature, humidity, cloud cover and wind. The heat index, which measures temperature and humidity, is less descriptive but easier to find on weather apps. Both explain why a shaded soccer field on a 90 degree F day (32 degree C) in arid Phoenix may be less risky than an exposed park on an 80 degree F (27 degree C) day in soupy Little Rock.
Just based on heat index, NOAA has a chart that calculates how dangerous prolonged exposure can be. For example, a day in which temperatures reach 96 degree F (36 degrees C) and 45% humidity would fall into the “danger” category for prolonged exposure or strenuous activity.
The WBGT threshold isn’t exact, but recent research suggests that even some young, healthy people can’t endure hours of exposure to high heat and humidity.
How to cool down
Overnight temperatures can be a particularly dangerous part of a heat wave, said Ashley Ward, director of the Heat Policy Innovation Hub at Duke University.
“Your body needs a reprieve,” she said. “You don’t get that overnight, we start the next day at a deficit.” Heat can worsen labor productivity and lead to more visits to the emergency room.
“When we have overnight temperatures that don’t drop below 75 degrees” F (24 degrees C), she said, “you start to see some pretty extraordinary outcomes with respect to heat illness and heat stroke, and even mortality.”
Ward said air conditioning can help, but she acknowledged that not everyone has access.
If you can’t afford to cool the whole house, Ward said, create a “cool corner” and sleep there, so your body is prepared to tackle the next day.
Evaporative or “swamp” coolers can help in dry heat, but they increase humidity and can make it more difficult to cool down. In humid places, just use a fan.
If you don’t have air conditioning, find public places that do, including movie theaters, malls and libraries. Some communities set up cooling centers.
Depending on where you live, the Low-Income Home Energy Assistance Program can help you buy a window air conditioning unit, according to the National Council on Aging. Some local nonprofits and civic organizations can also help.
Know your rights if you work outside
Knowing what workplace protections you have is important. Some states have them, including Washington, Oregon, California, Nevada, Colorado, Minnesota and Maryland, according to the Natural Resources Defense Council. Other states don’t have any.
If your state has work rules, try to learn them — though there are still challenges to ensuring regulations are actually enforced, said Bharat Venkat, director of the University of California, Los Angeles Heat Lab.
He notes that sometimes shaded areas are too far away for workers to take breaks without losing wages, or that management can make it impossible for workers to advocate for themselves. “Most workers don’t actually have control over their time or control over where they work,” Venkat said.
Within those constraints, finding ways to stay hydrated and lower your body temperature are important. You can do this by drinking lots of fluids, wetting clothing or putting cold water or a cold rag on your hands, feet, armpits and neck. A portable handheld fan or a cooling vest can also help.
If you’re exercising, avoid the hottest times of day and bring more water than you think you need.
