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Much of the U.S. will continue to see blazing heat this weekend

85 percent of residents in the Lower 48 could experience temperatures of 90 or higher

Daily temperature forecast through next Thursday from the National Weather Service. Boxed highs are record-threatening. (weatherbell.com)

More than 80 million Americans remain under heat alerts as punishingly high temperatures keep their grip on the Lower 48 through the weekend.

Readings near or past 100 degrees stretch from the border of Mexico to the border of Canada on Friday. Over the next week, 85 percent of residents in the Lower 48 could experience temperatures of 90 or higher, with nearly 20 percent reaching or surpassing 100.

Heat advisories centered on Missouri cover parts of 13 states in the central and southern Plains into the mid-South. Additional advisories are up for much of the northeast urban corridor. Excessive heat warnings are also in effect Friday for 10 million people in the desert Southwest.

Both Boston and New York City have changed triathlon plans for the weekend. In Boston, it’s been postponed until August, and New York City’s has been shortened by about half.

Farther south, Washington, D.C., remains under a mayor-declared heat emergency through Monday. Pools in the city will be open late, while shelters and cooling centers are also available.

In Texas and much of the southern Plains, farmers and ranchers are struggling with scorched fields and stressed livestock. The persistence of hot and dry conditions is unheard of in parts of the region.

Dozens of record highs have already been breached in the past several days, and about three-dozen may be threatened through the weekend. Numerous records for warm lows are also likely.

Scorching Southwest

An excessive heat warning is up for a big chunk of the desert Southwest on Friday, including Phoenix, Las Vegas and Palm Springs, Calif.

“Well above normal high temperatures will likely top out at 110 to 115 degrees today for Phoenix and all lower desert communities across the region,” wrote the Weather Service there.

This is on the heels of a number of record highs Thursday. They include Barstow, Calif., at 112; Bishop, Calif., at 106; and Desert Rock, Nev., at 108. A record high minimum of 90 was also tied in Las Vegas. In Needles, Calif., the overnight low was a remarkable 95 on Wednesday.

Friday is probably the last of this current bout of excessive heat for the region, as temperatures thereafter settle back toward normal levels nearer 100. Moisture associated with the summertime monsoon — a shift in winds bringing rain to the region — is slated to increase, helping build clouds and lower temperatures.

Sunbaked South

Across the Southern Plains and into the Mid-South, temperatures of 100 or higher have been the norm for weeks. Long-term drought and the spread of a flash drought are only magnifying the feedback loop between dry and hot conditions.

A slew of record highs fell across Texas on Thursday, including San Antonio, where it reached 102. It was the fifth record high there this month, on top of eight record highs in June and eight in May. The city has now seen 42 days at or above 100 in 2022, compared to an average of 19 for a whole summer.

San Antonio had 17 days of triple-digit heat in June. The norm is two.

Additional record highs Thursday included Houston (at Hobby Airport) with 100, Austin at 103, and College Station at 105. Numerous locations in Texas, such as Abilene and Dallas, also set record warm minimums for the date.

Record highs and record high minimums also occurred in Louisiana, Arkansas, Oklahoma and Missouri on Thursday.

Mercury rises in the Mid-Atlantic and Northeast

While the Northeast has avoided extensive heat so far this summer, the region is experiencing its hottest weather of the season thus far through the weekend.

Boston, Providence and Hartford, as well as coastal areas such as Cape Cod, are under heat advisories Saturday and Sunday. Temperatures inland are forecast to reach record-challenging highs in the mid-90s to around 100, while cooler locations near the shore also rise to near or above 90.

It’s a similar story in New York City and Philadelphia, where a heat advisory runs from Friday through Sunday, and each day should see readings reach at least the mid- and upper 90s.

“There will be a chance that a few spots could reach excessive heat warnings Sunday, and this will need to be monitored for in subsequent forecasts,” wrote NWS New York City.

Urban New Jersey and portions of New York City are at the greatest risk for reaching heat-warning criteria, which includes heat index values approaching 110. Newark, in the middle of a major urban heat island, has hit 100 twice this week.

D.C. heat wave: It could hit 100 for first time in six years Sunday

From the D.C. and Baltimore metro areas to Richmond, temperatures will rise into the mid-90s on Friday, with upper 90s to near 100 this weekend. Additional heat alerts seem like a good bet for these areas.

Numerous record highs are in play before a cold front brings a temporary halt to the brutal temperatures early next week. Sunday is likely the hottest day of the stretch, and many records may fall.

In addition to hot daytime temperatures, relief at night will be minimal. Temperatures in urban areas may not get much below 80, as others fall deeper into the 70s.

A return of Northwest heat next week

So far, this summer has been comparatively tame in much of the Pacific Northwest. But high pressure building into the area from the Gulf of Alaska early next week sets the stage for the hottest weather of the year so far.

“Western Washington will experience an extended period of well-above-normal temperatures and dry conditions through the long term,” wrote NWS Seattle.

Pacific Northwest heat wave in 2021 was ‘virtually impossible’ without climate change, scientists find

Hot weather takes over Monday and lasts much of the workweek. With temperatures in the 90s during the days, heat alerts may be enacted in parts of the area as the forecast closes in.

Why so hot?

A large “heat dome” of high pressure has been anchored across the southern United States for weeks. At times, it has expanded to reach the West Coast and East Coast.

Sinking air in high pressure tends to stymie cloud and thunderstorm development, maximizing the amount of summer sun beating down. Just over half of the Lower 48 is under drought conditions, per the U.S. drought monitor update released Thursday. Nearly 70 percent is categorized as at least abnormally dry.

Drought and high pressure tend to go hand in hand. The extended stay of the heat dome has helped keep drought going and temperatures high.

Britain’s freakish heat demolished records. Here’s what happened.

Human-driven climate change is also magnifying the heat. Temperatures tend to run a few degrees warmer than they might otherwise have without it and that’s been underscored in this summer’s weather in the United States and worldwide.

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