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Punishing heat waves peaking in Northwest and Northeast to ease this weekend

The heat domes responsible for record-breaking temperatures are set to sink south

Daily temperatures compared with normal temperatures. High heat is parked over the Northwest and Northeast on Friday. (WeatherBell)

Dueling heat waves continued to roast the Lower 48 as more than 100 million people remained under heat alerts on Friday.

Twin heat domes, or high-pressure system, have baked large parts of the country since midweek, setting numerous records. One heat dome on the West Coast was flexing across the Northwest on Friday and is expected to sink south this weekend. The other, centered near the Mid-Atlantic states, was pumping hot air over the central and eastern United States and will also retreat to the south over the weekend.

Heat wave blasts U.S., with 150 million Americans under alerts Thursday

The heat waves follow several others this summer, including an unprecedented late-June event that delivered numerous all-time highs to the Pacific Northwest. Both corners of the contiguous United States have endured abnormally hot weather this summer. Climate change is boosting the intensity and frequency of such events.

Pacific Northwest heat

The heat event is peaking in Washington, Oregon, Northern California and western Idaho. Excessive-heat warnings for these areas are in place for Friday and Saturday.

Record highs are anticipated Friday in Seattle and Portland. Other locations in Washington state expecting record highs include Olympia and Yakima.

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Temperatures in Portland are slated to top 100 degrees for a second day in a row. With five days at or above 100 this year, the city is tied with 1941 and 1977 for the most 100-degree days in a summer. One more 100-degree day, perhaps Friday, would mean 2021 stands alone on top of the list.

On Thursday, Bellingham, Wash., hit 100 for the first time on record. This is quite remarkable for a location 80 miles north of Seattle, on the water. It topped the old all-time maximum of 99 set during the June heat wave, among numerous other all-time records set across the region this year.

A sample of record highs on Thursday:

  • Eugene, Ore. — 104 degrees
  • Redmond, Ore. — 101 degrees
  • Vancouver, Wash. — 103 degrees
  • Portland — 102 degrees (tie)
  • Bellingham — 100 degrees (all-time)
  • Olympia — 96 degrees (tie)
  • South Lake Tahoe, Calif. — 90 degrees

Severe heat has also been occurring north of the international border. Several all-time monthly highs for August were set Thursday in British Columbia, including at Port Alberni and Abbotsford.

In addition to the extreme heat, places like Seattle will be dealing with smoky skies thanks to numerous wildfires in the region, coupled with the hot land-to-sea flow. Smoke has been an issue across the country, but particularly in the Pacific Northwest, in recent weeks. The combination of excessive heat and extreme drought have intensified conditions ripe for fires across much of the West.

The local Weather Service expects sky conditions to improve in and around Seattle this weekend as the wind direction shifts.

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The core of the heat wave will drop south this weekend. Excessive-heat watches are up for portions of Southern California and neighboring Nevada from Saturday through Monday.

Temperatures are forecast to rise into the 100-to-110-degree range for much of Southern California and the Central Valley to the north this weekend into early next week. The hottest day across this area appears likely to be Sunday.

Heading into next week, temperatures in California and neighboring areas will dip back to the 90s to around 100, except in typically hotter locations of the desert.

Northeast U.S. heat

Excessive-heat warnings are up for Friday in southeastern Pennsylvania and much of New Jersey, including the Philadelphia metro area. Heat advisories run from North Carolina up the coast to Maine.

Friday is the final day of significant heat on the East Coast in this episode. When a cold front sweeps through on Saturday, many spots will have seen a week straight of hot conditions. Even Saturday will be cooler, if not truly cool, thanks to the front bringing more clouds, with some storms, and eventually displacing the hot air.

A number of record highs are anticipated in the Mid-Atlantic and Northeast on Friday, in places such as Bridgeport, Conn., and Annapolis and in parts of the New York City region. Widespread readings in the mid-90s to around 100 are a good bet from North Carolina to southern New England.

This is on the heels of a number of record highs Thursday, a sample of which is below:

  • Dulles, Va. — 100 degrees
  • Newark — 98 degrees (tie)
  • Lynchburg, Va. — 98 degrees (tie)
  • Roanoke — 96 degrees (tie)
  • Elkins, W.Va. — 92 degrees
  • Islip, N.Y. — 90 degrees (tie)

In addition to record highs, extreme humidity has helped set a number of record-high low temperatures.

On Thursday, record high minimums were recorded in Bridgeport; Houlton, Maine; and Watertown, N.Y., among other locations. Places such as D.C. also recorded morning lows in the 80s on Friday, which is quite unusual historically. Additional record-high minimums are probable Friday and perhaps Saturday.

Hot nights have increased at a startling rate in D.C.

Saturday will feature cooler air spilling into western parts of the Northeast, while more typical summertime heat is squashed near the coast and deeper into the Mid-Atlantic and Southeast. Fairly widespread clouds and rain with the front should keep records to a minimum Saturday.

By Sunday, comparatively refreshing air will have taken over much of the northeast. That cooler air may be short-lived as warmer-than-normal temperatures are anticipated to return later next week.

More on heat waves

Our warming climate: It’s not just you ⁠— summers in the U.S. are getting hotter, and experts say heat waves will likely become even more frequent and intense. Take a look at what extreme heat does to the human body.

How to stay safe: It’s better to prepare for extreme heat before you’re in it. Here’s our guide to bracing for a heat wave, tips for staying cool even if you don’t have air conditioning, and what to know about animal safety during extreme heat. Traveling during a heat wave isn’t ideal, but here’s what to do if you are.

Understanding the science: Sprawling zones of high pressure called heat domes fuel heat waves. Here’s how they work. You can also read more about the link between weather disasters and climate change, and how leaders in the U.S. and Europe are responding to heat.

Tell the Post: What questions do you have about extreme heat, wildfires, droughts or other climate-related topics?