United States

By Brian Edwards, Meteorologist

August 17, 2012; 3:52 AM

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Millions of residents from the Midwest to the Appalachians will experience a roller coaster of temperatures later this week and this weekend.

A September-like air mass will dive down from Canada behind a potent cold front later this week and this weekend, bringing a refreshing blast of fall-like temperatures to many.

After a summer of numerous heat waves and records smashed, many residents and visitors will welcome the blast of cool air.

The chill will start on Thursday in the northern Plains with high temperatures struggling to reach the 70-degree mark in Fargo, Minneapolis, Bismarck and Rapid City. Add in a gusty northerly wind and low humidity values, and it will feel just like a late-September afternoon.

By Friday, the cool air will filter into Chicago, Rockford and Milwaukee. High temperatures will rise into the upper 60s and low 70s as the humidity plummets. Combine these temperatures with wind gusts to 30 mph and it will feel downright cool compared to the heat most experienced earlier this summer.

The cool air will continue its trek eastward Friday and Saturday, creeping into Detroit, Indianapolis, Pittsburgh and Cleveland.

Below is a chart of forecast high temperatures Wednesday through Saturday:

Not only will afternoon high temperatures remain on the chilly side, but overnight lows over much of the Midwest will reach record levels.

Current record low temperature values for Thursday and Friday range from the middle 40s to lower 50s from Fargo through Peoria and Omaha.

By Thursday night, actual overnight lows will fall into the 40s from North Dakota through Minnesota and parts of Wisconsin.

Friday night looks to be the best night as the winds die off, which combined with clear skies will lead to idea conditions for radiational cooling. Overnight lows Friday night will fall into the 30s over northern Minnesota with 40s all the way down to northern Missouri and the western suburbs of Chicago.

An air mass like this in mid-August will more than likely break dozens of low temperature records.

Though many people will be happy about the fall-like weather from the Midwest to the Great Lakes, residents farther east across the I-95 corridor will have to wait a bit longer for the really refreshing air.

The same front which is responsible for the fall chill will move through NYC, Philadelphia, Baltimore and Washington, D.C., later Saturday and Saturday night.

However, the air behind the front will have modified so much tracking east that it will bring temperatures closer to normal for mid-August standards.

Stay tuned to AccuWeather.com as we continue to track the first few blasts of fall-like air. Also, check with our AccuWeather.com Severe Weather Center for more information on a potentially dangerous outbreak forecast for the mid-Atlantic on Tuesday.