The South and Southwest hit record temperatures over the weekend and meteorologists warned that heat will rise in the East and High Plains.

Downtown Phoenix reached 111 degrees Fahrenheit on Tuesday
Credit…Adriana Zehbrauskas for The New York Times

For much of the United States, the last several days have been brutal: record temperatures recorded around the country, and coronavirus case numbers are on the rise as well, complicating efforts to protect people at risk.

The weekend set temperature records in the South and Southwest, which continued into this week. On Monday, the National Weather Service warned that “The relentless heat and humidity across the south-central U.S. will continue to make weather headlines going through the middle of the week.” On Wednesday, the Weather Service said that the most punishing heat would begin to abate across the South, but, like a hot bubble under the nation’s wallpaper, “will be on the increase for the eastern U.S. and for the northern High Plains.”

Greg Carbin, the chief of the forecast operations branch at the National Oceanic and Atmospheric Administration’s Weather Prediction Center, said, “It’s July — you kind of expect this, to some extent. But the magnitude of it is a little severe.”

This is the beginning of a summer that NOAA has warned is likely to have many more scorching days.

The combination of heat and humidity sent heat indexes in places like central Oklahoma above 115 degrees, and “that is just really dangerous to spend any time outdoors in, unless you’re standing under a cool waterfall somewhere,” Mr. Carbin said, who also noted that the heat index in New Orleans on Monday was 120 degrees. The tremendous heat and moisture can also set the stage for severe weather. “When you have that much energy available for those storms, it can be very dangerous,” he said.

Work on a concrete walkway in Austin, Texas. Temperatures broke a record for the day on Monday.
Credit…Tamir Kalifa for The New York Times

The heat wave is consistent with what scientists say to expect from climate change, said J. Marshall Shepherd, a meteorologist at the University of Georgia and a former president of the American Meteorological Society. He took part in a 2016 report by the National Academy of Sciences that found that, of the weather phenomena affected by climate change, heat waves show the strongest signal of the warming planet.

He compared the process to fertilizing a lawn. Grass will grow naturally, but “when we put fertilizer in the soil, it grows differently,” he said, and so “the natural cycle of heat waves is fertilized by anthropogenic climate change.”

The heat wave has been playing out across the South and Southwest in shared misery. On Monday, the National Weather Service in San Antonio announced the temperature reached 106 degrees, tying the July temperature record. Monitors at Phoenix’s Sky Harbor airport hit a blazing 114, matching a record hit previously in 2005, 2003, 1989 and 1939.

In Houston, Matt Lanza, a meteorologist for Space City Weatherreported the temperature at Bush Intercontinental Airport reached 100 degrees, with a heat index of 111. How does that feel? Such temperatures overwhelm the everyday vocabulary; in an exchange of Twitter messages, he called the combination of heat and humidity “terribad.”

Matthew Lara, a spokesman for the City of Austin Office of Homeland Security and Emergency Management, said that Monday’s high of 108 degrees — a record for that day by three degrees — underplayed the compounding effects of a city’s heat islands, where buildings and paved surfaces can amplify heat, temperatures can be much higher.

A park in Chandler, Ariz., outside Phoenix on Tuesday. The high was 111 degrees.
Credit…Adriana Zehbrauskas for The New York Times

Energy demand goes up during heat waves, and with so many people working from home that surge may be compounded by the rise in residential energy use, said Christopher Jones, director of the CoolClimate Network, a research consortium at the University of California, Berkeley. In general, heating and cooling homes is less efficient than it is for offices, he said. That would add to the power load, especially since so many of the office buildings people work in are still being cooled, as well. Heat waves lead to peak energy use, he said, which is “dirtier energy” since the plants that power companies bring online only when they need them tend to pollute heavily. The extra stress on the system also raises, “the potential for outages that can shut down the economy even further,” he said.

Weather like this disproportionally affects the vulnerable: people without the means to buy an air-conditioner or crank it up to full blast. Many cities have typically had cooling centers, where people can get out of the heat, often in places like community recreation centers. The coronavirus has introduced complications, Mr. Lara said, because the city’s cooling centers now require visitors to maintain social distancing and to wear masks. “You don’t want to cram 30 people into a room and call it a cooling center,” he said.

In Maricopa County, Ariz., county spokesman Ron Coleman said that the county has added to its collection of daytime cooling stations and land set aside for homeless people to pitch tents where they can have access to hand washing stations and portable toilets. The county has also opened a temporary overnight cooling shelter, and for those who appear to be at high risk for the coronavirus or who may have been exposed, the county has more than 200 hotel rooms “so we can have those individuals out of the heat and away from the congregate living,” he said.

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