Updated Jun 13, 2022 - Energy & Environment

Record-breaking heat wave envelops nearly 130 million in U.S.

Computer model projection of the "misery index" of heat plus humidity, showing the heat wave in the Central U.S.
Computer model projection of the "misery index" of heat plus humidity, showing the heat wave in the Central U.S. on June 13. Image: Earth.nullschool.net

More than 125 million Americans are under heat warnings and advisories on Monday evening as a dangerous heat wave that began in the Southwest covers more real estate in the Central and Southern U.S.

The big picture: The National Weather Service (NWS) is warning that a "dangerous" combination of heat and humidity will affect the majority of the lower 48 states before the week is over, and there are few signs the heat will abate after that.

  • All of Arkansas, Kentucky, Missouri, Mississippi, Illinois, Iowa and Indiana are under heat warnings plus parts of at least a dozen other states.
  • The heat wave is courtesy of a strong area of high pressure, or heat dome, that is slowly moving east across the Central U.S.
  • The heat dome is likely to shift eastward during the first part of the week, but then careen back west in a see-saw pattern, setting up hotter conditions again for the Upper Plains and Central states later in the week.
  • Climate change is causing heat waves such as this one to be more severe, frequent and longer-lasting than just a few decades ago.

Why it matters: Heat waves are the deadliest type of severe weather hazard in the U.S., and they especially target low-income residents who may lack access to air conditioning. They are also particularly dangerous for outdoor workers.

Threat level: As of Monday morning, heat watches, advisories and warnings were in effect from the Carolinas to Texas, extending north into Wisconsin and Minnesota and south to the Gulf Coast.

  • An early-season excessive heat warning is in effect for Minneapolis on Tuesday, when heat indices (the combination of heat and humidity) are expected to climb as high as 105°F.
  • According to Axios Minneapolis' Nick Halter, the city's public school district will close 14 schools on Tuesday that don't have air conditioning, and move those students to e-learning. City schools are still in session to make up for a three-week teacher strike in the spring.
  • Highs in many places, including Chicago; Des Moines, Iowa; St. Louis; Little Rock, Arkansas; and Memphis, Tennessee, are likely to hit 100°F today and tomorrow, threatening heat records.
  • High temperatures will be 20°F to 30°F above average for this time of year in many locations.

Of note: For the Central states, this will be a prolonged event. The lack of nighttime heat relief, with many records set for warmest overnight temperatures, raises the health risks associated with it.

  • "This is serious heat, so don`t underestimate it," the NWS forecast office in Memphis states on its website. "Stay indoors if possible. Forget strenuous activities outdoors during the heat of the day."

By the numbers: Forecast highs in multiple cities illustrate the severity of this extreme heat event.

  • 98°F: Forecast high temperature Monday in Memphis. The heat index there is expected to exceed 110°F, as dew points are running at tropical levels in the low 80s. For perspective, anything above a 70°F dew point feels sultry.
  • 100°F: Forecast high temperature in Denver on Monday, which would be the second triple-digit reading there since the heat wave began.
  • 97°F: Forecast high temperature in Chicago on Tuesday, which is about 30°F above average for this time of year.

Meanwhile, along with the extreme heat, wildfires broke out this weekend in Arizona, New Mexico, California and Colorado.

  • "Critical" fire weather conditions are expected Monday from the Southwest to the southern and central Rockies to the High Plains, NWS said.
  • The highest fire danger on Monday will be across a four-state region already hit hard by fires this year, including Colorado, New Mexico, Arizona and Utah.
  • High winds will hit parts of Southern California, increasing the fire threat there.

The bottom line: This is no ordinary June heat wave, and the NWS is urging residents in its path to take it seriously.

Editor's note: This story has been updated to reflect the most current heat warnings.

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