U.S. Coasts Will Share the Dangerous Heat This Weekend

For the third weekend in a row, an unyielding heat wave will bring dangerous temperatures to much of the United States, with warnings this time stretching from the desert Southwest to coastal New England.

The most enduring misery continues to be focused on central and southern states, including Missouri, Arkansas, Oklahoma, Kansas and Texas, which will “yet again” see temperatures in the 90s and low 100s this weekend, said Andrew Orrison, a meteorologist with the National Weather Service.

“We’ve had heat waves that have been quite long in the past,” Mr. Orrison said, but added, “This one here is pretty persistent, especially for parts of the central United States and in the Southern Plains.”

Here’s how other regions of the country are faring:

Northeast and Mid-Atlantic

Excessive heat set in earlier this week after a relatively mild summer. Temperatures will steadily rise to a crescendo on Sunday, peaking at around 100 degrees. The heat index — a measure of how humidity makes the air feel — will rise to 105. Washington could see its first 100-degree day in six years on Sunday.

After Monday, the Northeast could see some respite next week, with highs back down around 90.

Pacific Northwest

After also experiencing a relatively mild summer, heat will set in across much of the region on Sunday and into next week. Away from the coast, the highs will be in the 90s in Washington State, Oregon and Northern California and could reach 100 degrees. In Canada, British Columbia will also see a hot stretch.

Heat in the Pacific Northwest is particularly dangerous, because the usually temperate climate means that fewer people are accustomed to it or own air-conditioners. Last year, more than 600 people died in a heat wave that overtook the region for weeks.

Southwest

This will be the hottest part of the country on Friday. The interior deserts from Phoenix to Las Vegas are under excessive heat warnings, said Brian Planz, a Weather Service meteorologist in Nevada.

Las Vegas could see a high of 112 on Friday, about six degrees above normal, for this time of year. Phoenix is predicted to reach 114 degrees. But a monsoon predicted for the weekend will likely bring some relief, Mr. Planz said.

Nightfall in the desert is failing to cool things off much. The overnight low on Thursday in Needles, Calif., in the Mohave Valley, was 95 degrees.