WGN-TV Chief Meteorologist Tom Skilling and the WGN Weather Center staff provide daily coverage of weather in the Chicago area.

Dailey: July 2009 Archives

A southwesterly breeze develops Monday, bringing perhaps the warmest readings in three weeks to the area. Chicago's last official high of 86 degrees was recorded back on July 6. It will be close, but that high could be matched or even exceeded in spots across Chicagoland.
A cold front will move slowly through northeastern Illinois Tuesday accompanied by showers and thunderstorms, including some downpours. After that front moves east, cooler and less humid Canadian-source air will flow into the area, and high temperatures will probably fail to reach 80 degrees the rest of the workweek. Thus far, this July is tied with July 1924 as Chicago's fifth-coolest on record since 1871. All of the cooler Julys occurred prior to the 20th century when official observations were taken at various downtown locations near the lakefront.

U.S. weather extremes Sunday
The southwestern U.S. was scorched Sunday with temperatures peaking well above 100 degrees from southern California into Texas. Elsewhere, severe storms featuring funnel clouds, damaging winds and large hail hit the East Coast from Virginia to Massachusetts. Eight people were injured in Readington, N.J., when high winds hit a hot air balloon festival.

Computer models predict a continuation of the persistent upper air pattern that has steered cool Canadian air into the Midwest. Monday southwest winds will briefly boost temperatures into the mid 80s over northern Illinois ahead of an approaching cold front. However this warming will be short-lived, as the cold front sinks into southern Illinois and cooler air returns after another bout of showers and thunderstorms Tuesday. The remainder of the week there will be only minor day to day variations in temperatures with highs averaging about 3 degrees below the seasonal norms.

Potential for Chicago's coldest July since 1891

As of July 25th this July's official Chicago temperatures have averaged 4.4 degrees below normal. If readings for the month end up averaging 4 degrees below normal, this July will be the sixth coldest on record dating back to 1871 and the coldest since 1891. All five of the coldest July's occurred prior to the 20th century when official observations for the city were taken at various locations downtown near Lake Michigan.

Warm-up doesn't last, turning cooler last half of the week

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The latest attempt at a warm-up in Chicago looks like it will be short-lived. Canadian-source high pressure will hold Monday, continuing a cooling weak northeast wind off Lake Michigan. As the high moves east, winds pick up from the southeast and finally become southwest later Tuesday, allowing warm, moist air to feed into northern Illinois.  The approach of a cold front from the northwest will trigger a band of showers and thunderstorms which should hit the Chicago area Tuesday night and early Wednesday. Cool dry high pressure will follow the cold front and hold sway over the Midwest and Great Lakes into next weekend. The southern third of the United States will continue to swelter--in the 90s across the Southeast and more than 100 degrees in the Southwest.
Cool temps not really that unusual here
While this summer has been cool, a closer look at Chicago's 139 years of records shows that the overall average temperatures during the first half of summer 2009 actually barely fall in the coolest third with 91 warmer and 47 cooler. In the 51 years of observations at O'Hare Airport, 2009 ranks as the 14th coolest.