As many as 49 million people are under heat alerts Monday spanning three distinct areas: the Northeast, the Plains stretching into portions of the South, and the Pacific Northwest.
Monday will be the last in this band of excessively hot days across the mid-Atlantic and the Northeast after what was a blazing hot weekend.
As of Sunday, New York City had recorded temperatures of 90 degrees Fahrenheit or higher for six straight days. If the Big Apple hits 90 Monday, it will be the the longest heat wave since 2013.
LaGuardia Airport hit a new record this week with five straight days of temperatures soaring to 96 degrees or higher.
In nearby Newark, New Jersey, temperatures reached 100 degrees for five straight days in a row, an astonishing record never recorded in the city before.
Boston also managed to hit triple digits Sunday, and Washington, D.C., still had a heat index value of 98 degrees as late as 10 p.m. Sunday.
There is, however, some good news on the horizon. Monday will be the last excessively hot day in the Northeast, before the heat breaks Tuesday. But heat alerts remain posted from Maryland to Boston on Monday as heat indexes are expected to climb into the 100s in Philadelphia and Washington, and the upper 90s for New York City and Boston.
The heat will decrease significantly for much of the region Monday afternoon and evening as thunderstorms roll through. While the storms will be good for cooling temperatures, they may be severe and cause damage in some areas.
A total of 53 million people are under the threat of severe storms across the region. Damaging wind gusts are the primary threat as the storms hit Monday afternoon and evening from Virginia to Maine. There is the possibility of isolated tornadoes.
Major population centers along the Interstate 95 corridor will be in the risk zone during the evening commute.
Cities to watch: New York, Philadelphia, Baltimore, Boston and Washington.
While the Northeast can look forward to the heat breaking Tuesday, those in the southern Plains and the western portions of the Southeast won't catch a break from the excessive heat. High 90s and low 100s are on tap from Memphis, Tennessee, to Oklahoma City to San Antonio. Heat index values will range from 105 to more than 110 in much of these areas, with the Tulsa, Oklahoma, area expected to go as high as 112.
Dallas was forecast to hit its 30th 100-degree day of the year Monday.
Dangerous and prolonged heat also begins in the Pacific Northwest, as excessive heat warnings in parts of the region remain in effect through Thursday and Friday. Seattle is forecast to have four straight days of highs in the 90s from Tuesday through Friday, and the Portland, Oregon, area is expecting highs to top out in the low 100s Tuesday.
The hottest temperatures will be across interior portions of Washington state, forecast to climb as high as 115. Heat alerts currently stretch from Northern California up to the Canadian border.
While this heat event is not expected to be as intense as last summer’s deadly heat wave that impacted this region, meteorologists urged people to take alerts seriously.
Heat has also fueled the Oak Fire near Yosemite National Park. Over the weekend, the area surrounding the fire reached 96 degrees, and temperatures are expected to stay above the 90-degree mark for the rest of the week.
As of Monday morning, the fire had grown to 17,000 acres and was still zero percent contained.
Some good news: While the heat and low humidity will continue to fuel the fire, winds are expected to be light, which should help firefighting efforts.