More than 140 million people across the Midwest and Southeast were warned of dangerously high temperatures Tuesday as one of the biggest heat waves in years swept across more than a dozen states.
The heat, which has persisted for days, is expected to get worse as the week progresses, the National Weather Service said in a Tuesday update. Hot weather this time of year is to be expected, the agency said, but the approaching days of “searing” triple-digit temperatures combined with “brutal humidity levels” will make it feel as hot as 120 degrees in some places.
“While it is not uncommon for August to feature dangerous heat, these temperatures are extremely anomalous and likely to break numerous daily and potentially monthly records,” the NWS said. “In fact, highs are forecast to reach up to 20 degrees above average throughout Iowa and neighboring states over the next few days.”
Alerts ranging from heat advisories to excessive heat warnings are currently in place in 17 states across the Midwest and reaching down into the Southeast. More than 40% of the U.S. population is within the advisory and warning zones.
Several major cities are among those under heat warnings, including Chicago, St. Louis, Minneapolis, Kansas City, Nashville, Oklahoma City, Louisville, Dallas, Houston and New Orleans.
The NWS is forecasting that more than 90 record high temperatures will be broken over the next three days.
The agency’s branch for the greater Chicago area warned Tuesday afternoon that over the following two days, heat indexes, which reflect how hot it actually feels when both air temperature and humidity are accounted for ― are expected to climb as high as 115 degrees.
The NWS for the St. Louis region, which has been battling dangerously hot weather for days, said it’s already clocked that rarely seen high temperature.
“We’re only half-way through this heat wave, but it’s already one for the record books,” the agency tweeted. “We’ve only seen 14 days of 115F heat index values EVER, and one was this Sunday.”
The NWS office for the Kansas City area urged people to limit outdoor exposure as much as possible, saying the conditions are “untenable for even short durations,” and to wear light colors when spending time outside because they absorb less heat.
People shouldn’t expect much reprieve from the heat at sundown.
“Very warm overnight temperatures only dropping into the upper 70s and low 80s will compound the impacts associated with this potentially deadly heat wave,” the NWS warned.
Extreme heat waves, which wreak havoc on the body’s fluid supply, threatening kidney and other vital organ function, are the deadliest weather-related events. In most years, they kill more Americans than hurricanes, floods and tornadoes combined.
This week’s high temperature event is due to a high-pressure ridge, or a “heat dome,” stuck over the affected region and trapping hot air.
Last month was by far the hottest month ever recorded, European scientists reported earlier this month with a dire warning about the climate crisis. Scientists have found that climate change makes heat waves 150 times more likely.