Heat indexes are predicted to climb over 113 degrees in parts of Arkansas, Louisiana, Mississippi and Texas on Wednesday, with roughly 100 million people in the U.S. under an excessive heat warnings or heat advisories, according to the National Weather Service. Such warnings are impacting 28 states, ranging from California to New Hampshire.
The temperatures are so high that they may surpass what the human body can physically handle, Kim Knowlton, an assistant clinical professor of environmental health sciences at Columbia University, told NBC News. "There’s an awful lot of assumption that heat is an inconvenience, but it kills people," she said. "Climate change is fueling these dastardly heat waves that are almost beyond belief, and we’re not accustomed to them yet."
Here's how to stay safe in extreme heat.
Stay indoors and avoid heat
Start by limiting your outdoor activity: Kids shouldn't be playing outside in the heat of the day unless it's an activity like playing in the pool, where the water can lower their core temperature, Dr. Emily Durkin, pediatric surgeon with Spectrum Health in Grand Rapids, Michigan, told TODAY.
"Going to the park, that type of thing, is fine as long as you have the opportunity to get into the shade and take advantage of water activities," added Dr. Torree McGowan, an emergency physician in Oregon and a member of the American College of Emergency Physicians. "Those types of activities to decrease the heat can be really a lot of fun and safe, but we have to watch during the heat of the day."
Kate Dischino, the vice president of emergency programs at Americares, a disaster relief organization, said that people should take care to avoid "heat islands" — outdoor areas like blacktops where heat can be trapped and lead to higher temperatures.
If you are staying at home, do what you can to keep your house cool. McGowan said an issue in the Pacific Northwest is the lack of air conditioning in many homes, so people should try to keep out the sun and heat as much as possible. If you can't keep your home cool, take advantage of nearby cooling centers or air conditioned spaces like libraries or shopping malls.
One thing that all three experts highlighted is the need for proper hydration: While drinking a lot of water in the heat may seem obvious, it's also important to replace the electrolytes you lose when sweating.
"One of the biggest dangers during extreme heat like this is dehydration," said McGowan. "Our body keeps cool by sweating and you lose a ton of water during hot days like this when you're sweating a lot ... You lose water and electrolytes when you sweat so some type of sports drink can be really helpful to replace those lost electrolytes."
Sugary drinks and alcohol can be "really bad for you" in extreme heat, according to Durkin. It's also important to keep up your sodium levels, which can be impacted by sweating.
If you begin to feel nausea and stomach cramping, that's a sign of dehydration, Durkin said, which can lead to a "vicious cycle" since someone feeling ill might not want to drink liquid, which leads to further dehydration.
"The key is to recognize and stay hydrated before you develop those symptoms," she said. If you do develop those symptoms, try drinking; if they persist, seek medical attention. It's especially important to keep an eye on kids playing outside, since they may not think to pause for a drink.
Know what to do if the power goes out
Dischino referred to power outages as a "secondary" effect that can be caused by extreme heat: People using air conditioners and other power sources to cool down can overload a power grid, leading to blackouts. People should have a plan in place for where they'll go if they lose power and begin to get too hot.
Dischino also said that people who use medical equipment or other electronic devices should be prepared: If you have a battery powered alternative, make sure you have what you need to power it. If you need constant power, make sure you're near a cooling center or other place with power.
Keep an eye on medications
McGowan said that some medications can "impair your ability to tolerate the heat" and make users "even more prone to heat stress." The medications most likely to have these side effects include blood pressure medications and medicines to treat things like seizures.
"Anyone who takes these medications needs to be even more careful to make sure they're staying cool during this weather," said McGowan, noting that elderly people who are already more vulnerable to heat are more likely to be on these medicines.
Check in on neighbors
Dischino said that people should prepare to check in on vulnerable neighbors or family members. If you're someone who lives alone, try identifying a "buddy" who you can stay in contact with.
Know when to seek medical attention
Durkin said that having difficulty in perceiving temperature or someone feeling like they are getting cooler with no actual change in temperature are both signs that someone should seek medical attention.
Stomach cramps, nausea, feelings of weakness and dizziness are all also signs to "seek help right away," said Durkin, especially when reported by vulnerable populations like children or older adults. McGowan said that if people are having difficulty speaking, are slurring their words or are "getting confused and not making sense," that's another sign of heat-related illness.
"Obviously, this is a dangerous time period, and we just encourage everyone that if they're concerned we're always happy to see them in the emergency department," McGowan said. "The first step, if you think you're getting overheated, is to find a cool area, sit down, rest and drink lots of water. If that doesn't work, we're always happy to see them."