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Portland, Ore., soared to 116 degrees — hotter than Dallas, Miami and L.A. have ever been

On the other side of the country, Boston was forecast to hit nearly 100 degrees and New York City could feel like 105.

Portland, Oregon, soared to a searing 116 degrees Monday, hotter than it has ever been in cities such as Dallas, New Orleans and downtown Los Angeles. In fact, when it comes to major U.S. cities, only Phoenix and Las Vegas have been hotter.

On the other side of the country, a parallel heat wave was in full swing, with Boston forecast to touch 100 degrees Tuesday.

The culprit? A buckling in the jet stream causing amplified ridges to surge far north on both sides of the country, resulting in dangerous heat infiltrating areas unaccustomed to it. On Tuesday, 12 million Americans across much of the West were under heat watches and warnings, and 44 million were under heat alerts across the Northeast, stretching from Delaware to Maine.

Monday was a textbook example of a summer scorcher, pumping heat into the entirety of the Pacific Northwest and prompting an electrical utility in Spokane, Washington, to warn that people will face more rolling blackouts amid heavy power demand. More than 35 cities tied or set records, with many areas soaring an unprecedented 30 to 40 degrees above average. The record in Seattle was smashed by 5 degrees, hitting 108, and the record high in Portland was also shattered, soaring to a sizzling 116 degrees, 8 degrees higher than the old record.

The heat was so excessive that Portland streetcar power cables melted and the pavement buckled. And the heat has been so persistent that Seattle achieved a new record: three consecutive days of triple-digit temperatures for the first time.

The historic heat even jeopardized several state and national records. The record high of 119 for Oregon and the record of 118 in Washington came nearly within reach when Salem, Oregon, hit 117 and Dallesport, Washington, hit 118 Monday.

Most impressive, Lytton, British Columbia, recorded a high temperature of 118 degrees, establishing a new national record for Canada, and crushing the old record by 5 degrees. This temperature surpassed Las Vegas' all-time high of 117.

To put this extreme heat into perspective, the hottest temperatures in traditionally hot cities are still cooler than these new records for Portland and Seattle. Miami’s record high is a mere 100 and Atlanta's is only 106.

On Tuesday, the Northwest cities of Seattle; Portland; Boise, Idaho; Billings, Montana; and Reno, Nevada, are expected to continue to experience temperatures in the triple digits, and the Pacific Northwest humidity will drive these temperatures to feel like the 110s.

Imamge: People cope with record-breaking heat in Portland, Ore.
People cope with record-breaking heat in Portland, Ore.M. Staab; J. Rudoff; K. Elsesser; A.M. Tracy / Bloomberg via Getty; SIPA via AP; AFP via Getty; SIPA via AP

In the Pacific Northwest, temperatures will start to cool off Tuesday and Wednesday near the coast, but it will remain scorching hot in the interior, as the cooling breeze off the Pacific Ocean won’t reach sufficiently far inland. Tuesday will be the first in three days that the forecast high is below 100 for Portland and Seattle, but temperatures will remain in the 90s, 10 to 15 degrees above average. Glasgow and Helena, Montana, Boise and Spokane, Washington, can expect triple digits through the Fourth of July.

About 8,200 utility customers in parts of Spokane lost power on Monday, and Avista Utilities warned that there will be more rolling blackouts on Tuesday in the city of about 220,000 people, with the high temperature predicted at 110 degrees, which would be a record.

Avista had planned for much higher than normal demand but hit its limit quicker than anticipated because of the intense heat, Heather Rosentrater, the company's senior vice president for energy delivery, said Monday.

Daily records could also be broken across New England as temperatures were expected to reach well over 100.

Heat warnings cover much of New Jersey, and extend over Philadelphia. New York City will likely see its hottest temperatures so far this year, and Philadelphia and Boston have already declared heat emergencies. This is truly rare heat; New York City averages just a few days a year with temperatures above 95 degrees.

Temperatures moderate slightly through the end of the workweek, returning to about average by the weekend.

Summers are getting hotter in the Pacific Northwest as a result of climate change, with most cities feeling 2.5 to 3 degrees hotter than they did in 1970. As carbon dioxide levels rise and climate change progresses, more extreme and more frequent heat waves can be expected for unprepared cities across the country.