European model simulation indicating low pressure at high altitudes, signifying a pool of cold air, Friday, Aug. 4. (WeatherBell.com)

The first of several deep pools of cold air dropped into the Upper Midwest on Thursday, ushering in a period of below-normal temperatures for the next 10 to 14 days for the eastern two-thirds of the country.

In Wisconsin and Michigan on Friday, shorts were swapped for sweaters as high temperatures hovered around 60 degrees — some 15 to 30 degrees below normal.


Temperature difference from normal simulated by GFS model Friday afternoon, Aug. 4. (PivotalWeather.com)

Some temperatures at 1 p.m. Friday:

  • Madison: 61 degrees
  • Milwaukee: 62 degrees
  • Green Bay: 60 degrees
  • Chicago: 62 degrees

These are much more typical of early October than early August.

Some of this cool air will spread toward the Mid Atlantic and Northeast this weekend, although its intensity will lessen. Saturday afternoon temperatures are predicted to be 5 to 15 degrees below normal, in the 70s north to low 80s south.


GFS model forecast of temperature difference from normal in the Mid-Atlantic and parts of the Northeast on Saturday, Aug. 5.

From the Midwest to the East Coast, the current push of cool air will be brief, but additional cold fronts are predicted to sweep across these same areas between Monday and Tuesday, and potentially late next week. In between these cold fronts, temperatures should temporarily rebound to near normal levels. But, on balance, cooler than normal weather is expected — especially in the middle of the nation.

The National Weather Service’s six to 10 day outlook presents deep blues over the Central U.S. – conveying a high likelihood of cooler than normal air prevailing. Lighter shades of blue extend toward the East Coast suggesting the odds are tilted toward cooler temperatures, but they’re not a definite.


National Weather Service 6-10 day temperature outlook.

This pattern is expected to persist through mid-August, but there are some signs it will reverse later in the month — which would then favor warmer-than-normal temperatures in the eastern two-thirds of the nation.