More than 125 million people are on high alert in the United States

Editor’s Note: A version of this article originally appeared in the weekly weather newsletter, the CNN Weather Brief, which is published every Monday. You can sign up here to receive them every week and during severe thunderstorms.


This is exceptionally hot and humid for any time of the year.


“We don’t change our criteria based on the time of year,” Matt Beitscher, a meteorologist with the National Weather Service in St. Louis, told CNN Weather.

A heat dome that began last week in the southwest has moved to the central United States, where heat and humidity will rise together to levels that will have a significant impact on the human body.

“This is a day when not only people who are susceptible to heat-related illnesses, but actually anyone who will be outside for an extended period of time is at risk for heat-related illness,” Beitscher said.

More than 125 million people are on heat warnings, which include excessive heat warnings and heat warnings, across much of the central and eastern states on Monday evening. This is over a third of the US population. Cities under alert for excessive heat include Tulsa, Memphis, St. Louis, Minneapolis, Cincinnati, Raleigh, and Charlotte.

“Record heat is expected to spread from the Great Plains today, then into the Mississippi Valley and Southeast through midweek thanks to the expansion of a higher level ridge,” the Weather Prediction Center said Monday afternoon.

By Monday afternoon, daily high temperature records are already set in several cities, here are a few:

  • Columbia, South Carolina hit an afternoon high of 103 degrees, beating the old June 13 record of 102 degrees set in 1958.
  • North Platte, Nebraska, reached 108th, breaking the old record of 103th set in 1952
  • St. Louis, Missouri hit 100, beating the old record of 98 set in 1952
  • Charlotte, North Carolina, hit 98, breaking the old record of 97 set in 1958
  • Nashville, Tennessee reached 97th, equaling the previous record of 97th set in 2016
  • Jackson, Kentucky, scored 94th; the previous record was 91 in 2000
  • Asheville, North Carolina, reached 92nd; the previous record was 91 in 2016

The sweltering conditions will feel worse right in the middle of the country, putting the cities of Memphis and St. Louis in the highest risk category, “excessive heat warnings”.

“Having an excessive heat warning earlier in the year is pretty unusual,” said Mike Johnson, a meteorologist at Memphis NWS. “We issue excessive heat warnings maybe once or twice a year. It’s pretty rare because it requires a heat rating of 110 degrees.”

The Heat Index is a graph that combines humidity and heat to indicate how air actually feels for a human.

Take this southern meteorologist, when it’s this humid, you constantly seem like you’ve just run a marathon walking outside.

It’s because the air already has too much moisture and will prevent sweat from evaporating.

Evaporation is the process that cools your body. Hence, your body will not cool down when it is humid because there is nowhere for the sweat to go. It makes him feel much warmer than he is.

The reason behind the extremely high temperatures is a high pressure area that creates a transparent lid over the United States. The lid will trap any escaping radiation and send it back to the ground as the sun’s rays continue to penetrate through.

The terrible heatwave is even more dangerous because it is happening in June, close to the longest days of the year. The National Meteorological Service measures the temperature in the shade and the heat index is calculated using the shade reading. Thus, it will be even warmer in the direct sun.

It will feel “much, much worse in the sun than in the shade,” Beitscher noted. “These values ​​are kind of a reference, and then they get worse from there if you talk about the impact of the sun.”

To add insult to injury, don’t expect it to be hot one day and cool the next.

“This will be a long-term event and will not last just yesterday and today; it will go on for the whole week, ”Johnson said.

The muggy weather will continue to move further northeast in the upper Mississippi Valley, western Great Lakes, and Ohio Valley, while it will continue to grow over the southern Mid Atlantic and southeast on Tuesday, according to WPC forecasts.

“Few changes are expected on Wednesday, with many locations slated to see record consecutive days,” the WPC wrote.

Chicago could also see temperatures soar to nearly triple digits, allowing the heat index to easily exceed 100 degrees this week.

I hate being the bearer of even more suffocating news, but heatwaves are something we will have to get used to.

“Climate change is increasing the frequency and intensity of heat waves around the world, tipping the scale in the direction of warmer temperatures,” said Brandon Miller, CNN meteorologist and climate expert.

“In the United States, record high temperatures are now more than twice as likely to occur as record low temperatures,” according to the US National Climate Assessment.

“And while much of the country is cooking in the peak of summer heat even before the summer solstice arrives, major heat waves are also occurring in Europe and Asia at the same time,” Miller noted.

In Europe, heat is pumped north around a high pressure area, similar to what we are doing in the United States. It is bringing incessant heat to Spain and France for the rest of the week.

In France, it is likely to peak on Thursday and Friday. Spain, where it will last until at least Thursday, is also facing a surprising drought. Aridity, coupled with heat, is putting most of the country in “extreme” fire danger.

It is very similar to what is happening in New Mexico, where the threat of fire is once again critical, today and tomorrow.

And then there’s northwestern China, where temperatures will reach three digits Fahrenheit.

Another disaster is likely on the northern and northeastern edges of this thermal dome: a derecho could form.

To be called derecho, severe storms must have winds above 58 mph and cause damage that extends for at least 250 miles. The resulting conditions can be described as a tropical storm on land. Adam Smith, a climatologist with the National Oceanic and Atmospheric Administration, described a 2020 derecho to CNN Weather as an internal hurricane, with winds exceeding 100 mph and hurricane force winds lasting up to 45 minutes.

“Some of the most intense summer derechos, particularly the progressive ones, occur on the fringes of major heatwaves,” the SPC wrote on their website explaining the derechos.

Historically they occur at the edges of thermal domes, because the jet stream revolves around high pressure – the level of the atmosphere where jets fly and the current of stronger winds is found – up and around, which helps create instability.

But at noon on Monday, it was still unsure whether one will form later today.

Even if not, thunderstorms capable of hurricane wind gusts (75+ mph) could occur from Wisconsin through Ohio Monday afternoon and evening.

“There is a fairly widespread threat of wind damage tonight and at night,” CNN meteorologist Chad Myers said. “We are expecting bad weather watches and lots of warnings starting this afternoon. Indeed, this fast-moving cluster of storms could even be approaching Mid-Atlantic states by morning. ”