Heat to wane in Northeast as Pacific Northwest prepares to roast

Heat alerts blanket the Pacific Northwest, including much of Oregon and Washington state, where temperatures are set to spike to 110 degrees in the days ahead. Northern California will also be affected, the atmospheric blowtorch coming as wildfires, including the swiftly moving Oak Fire, have triggered evacuations and a state of emergency.

Daily high temperatures about 10 to 20 degrees above average will persist through at least the end of the workweek, with elevated highs sticking around into the weekend. Several records will be set. Heat index values could reach dangerous levels.

The episode coincides with the conclusion of a heat wave that brought highs in the upper 90s to near 100 in the Northeast and the Mid-Atlantic. Boston jumped to 100 degrees Sunday, something that happens only every couple of years on average. Newark hit the century mark for five consecutive days ending Sunday, the longest such streak on record, although there are questions about whether its temperature readings are reliable.

Excessive heat warnings and heat advisories from the National Weather Service affected about 65 million people in three regions of the Lower 48 on Monday: the coastal plain of the Northeast; portions of northern Texas and central and eastern Oklahoma through western Tennessee and northern Mississippi; and the Pacific Northwest, away from the coast.

In the days ahead, while the heat will ease in the Northeast, it will remain entrenched over the southcentral United States and will become more intense in the Pacific Northwest. The Weather Service emphasized particular concern for those without air conditioning — a significant percentage of residents in parts of Washington state, Oregon and Idaho. Only an estimated 44% of households in Seattle are air-conditioned, for example, and highs are expected to hit 90 degrees every day this week. The late July average in Seattle is 79 degrees.

Jacob DeFlitch, a meteorologist at the Weather Service in Seattle, said that although it’s not uncommon for Seattle to reach the 90s during the summer, the duration of this event will be unusual. He said Seattle could hit 90 on four straight days. Seattle’s record is five 90-degree days in a row.

“Residents without air conditioners will experience a [buildup] of heat within their home through late in the week,” the Weather Service wrote.

Especially hot will be the Columbia River Basin, where hot air pouring into the valley will experience even greater downsloping. Kennewick, Wash., southeast of Yakima, could spike to 113 degrees Thursday and Friday before a relative cool-down into the lower 100s by the weekend.