Residents across much of the United States sweating out the hot temperatures finally will get a break.
The Midwest and subsequently the East Coast will be getting cooler weather but also heavy rain and windy conditions.
"A cold front shifting across the Central Plains, Midwest, Great Lakes and Northeast on Sunday will bring some relief from the heat with cooler and drier air," the National Weather Service posted on Twitter. "Excessive heat holds Sunday roughly south of I-70. Heavy rain from thunderstorms along the front may bring flash flooding."
In the Midwest, overnight temperature dropped after hovering near 80 degrees in the past week.
"When an unusually strong cold front moves into an unusually hot and humid air mass, severe weather can be expected and that will be the case through Monday," AccuWeather Senior Meteorologist Adam Douty said.
"The strongest thunderstorms will produce flooding downpours and damaging wind gusts."
One such band of slow-moving heavy thunderstorms raised concerns for flooding over Chicago's southwestern suburbs Sunday.
Through Sunday night, thunderstorms will slice into the sweltering heat over parts of the interior Northeast and from the Lower Midwest states and back to the central Plains.
The area at greatest risk lies over Missouri and eastern Kansas. This includes the cities of Wichita and Topeka, Kan.; and Kansas City and Springfield, Mo.
The strongest thunderstorms in this region can also produce hail and an isolated tornado.
Drenching rain and thunderstorms will then focus on areas from the Ohio and Tennessee valleys to the Northeast on Monday.
The strongest thunderstorms can down trees and cause power outages from New York City to Philadelphia and Harrisburg, Pa.; Baltimore and Washington, D.C., during the afternoon and evening hours. The threat zone will also stretch down to Charlottesville, Va.
Severe storms across the Midwest and Great Lakes knocked out power to hundreds of thousands and caused widespread damage. On Sunday afternoon, in Michigan more than 454,000 out of 4.8 million customers were without power, and in Wisconsin there were more than 667,000 outages out of 2.5 million customers, according to Poweroutages.us.
More than 95 million people were under a heat warning or advisory for Sunday, which is down from Saturday's 157 million, CNN reported. Heat indices of 115 to 120 reached much of the nation Friday and Saturday.
The heat wave stretched from New Mexico to Maine. Across the country, cities and counties put out warnings and ways to to help deal with the heat.
"The temperatures we're seeing in our city today and tomorrow could be the highest we've seen in years. Take it seriously," New York City Mayor Bill de Blasio urged his city in Twitter post Saturday afternoon.
JFK International Airport and Atlantic City, N.J., set daily record highs at 99 degrees Saturday.
Other high temperatures, as reported by ABC News:
Hartford, Conn.: 110 degrees; actual high 95
Washington, D.C.: 108 degrees; actual high 97
Kansas City, Mo.: 109 degrees; actual high 98
Baltimore: 107 degrees; actual high 100
Boston: 107 degrees; actual high 97
Chicago: 107 degrees; actual high 95
Boston and Washington have another change of nearing 100 degrees.
The seasonable weather that has dominated the northwestern United States so far this month is coming to an end as heat surges northward through Tuesday.
"The area has generally been running pretty close to average this month without any major bouts of heat, so it seems like we're overdue for a warmup," AccuWeather Senior Meteorologist and western U.S. blogger Brian Thompson said.
A flip in the weather pattern will allow heat to surge northward over the interior West early this week, while residents in the Midwest and Northeast catch a break from oppressive conditions.
High temperatures will trend downward through Tuesday from their peak near 90 degrees in Portland and in the middle 80s in Seattle on Sunday.
At the same time, temperatures will crank up east of the Cascades toward the northern Rockies, according to Thompson.
Temperatures are forecast to be 5-10 degrees above normal in these areas.
Boise, Idaho, could come close to triple digits Sunday and hit or exceed the mark by Monday and Tuesday. The city hasn't hit triple digits. & Re