In the Northern states, a heat wave is loosely defined as three consecutive days where temperatures reach 90 F or higher. Most locations will over the Ohio Valley states will have two- to three days with high temperatures ranging from 85 to 90 degrees, including highs from Sunday, forward to Tuesday.
Much cooler air will continue to press eastward across the northern tier states and will cut the heat off.
RealFeel temperatures peaked just above 100 F in Chicago during the midday hours on Monday, prior to the arrival of a push of cool air from the northern Plains.
The heat is hitting at a time when college and some high school and elementary school students are back in the classroom.
The pattern will offer a chance for those who have time off to enjoy some extended summer weather, of which has been rather limited this season.
Temperatures have averaged below normal from St. Louis and Chicago to Detroit, Cincinnati and Pittsburgh since June 1.
The temperature has approached 90 degrees on only a handful of days this summer, the majority of which have been scattered through the season. As of Aug. 24, Indianapolis and Pittsburgh had not hit 90 this summer.
The RealFeel temperature hit 105 F at Indianapolis Monday afternoon as the actual temperature approached the 90-degree mark. Pittsburgh is unlikely to hit 90 in the pattern.
A spell of very warm weather will also occur in the East at midweek. Temperatures in some neighborhoods from Washington, D.C. to New York City and Boston could reach the 90-degree mark.
While the region received a break from rainfall at the start of the week, the risk will increase from northwest to southeast during the middle part of this week.
Showers and thunderstorms associated with a press of cooler air will mark an end to the heat and humidity over much of the region Tuesday through Thursday.
By Alex Sosnowski, Expert Senior Meteorologist for AccuWeather.com