Cool, Wet Start to September in Illinois

No surprise – the first half of September was very wet across much of Illinois. And it is raining across central Illinois as I write this.  Temperatures for the first half of September are 3 to 4 degrees below average in Illinois.

The first map show the accumulated precipitation for the Midwest. The largest precipitation totals occurred in western Illinois, southern Iowa, western and northern Missouri, as well as parts of eastern Nebraska and eastern Kansas. A second area of heavy precipitation occurred in northern Wisconsin and northern Michigan. For agriculture, having this much rain at the end of the growing season is probably not welcome.

The second map shows the temperature departures from average across the Midwest. For Illinois, the coolest departures from average occurred in western Illinois – no surprise due to all the rain and cloudiness there. Temperatures were cooler-than-average across the Corn Belt but the departures became increasingly stronger when moving westward and northward.


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Frost in Illinois – Not Quite Yet

While cold air moved in behind the low-pressure system that passed through the Midwest this week, it looks like Illinois will likely dodge the freezing temperatures for now. But someday they will come. Here are the median dates for when we see the temperatures drop to 32 or below in fall, as well as the earliest date in 1 out of 10 years.

In general, we hit 32 degrees in early October for northern Illinois and mid October for central and southern Illinois. In 1 year in 10, we have seen 32 degrees in the last week of September (second map) or the first few days of October. See more maps and discussion of frost on the State Climatologist web site.


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Heavy Rains in Western and Central Illinois

Heavy rains have fallen in western and central Illinois over the last three days. Here is the overall picture showing the heavy rains in southern Iowa and northern Missouri as well. Areas in yellow, orange, and red experienced 2.5 to 8 inches of rain. Much of the rest of Illinois received 1 to 2 inches. ridge2 RFC_Precip

3-day Rainfall Totals based on radar and rain gauge measurements. Click to enlarge. Source:

The largest three-day total comes out of Rushville with 8.06 inches with most of that falling on one day (6.96 inches on September 10). To put that in perspective, the average September rainfall at Rushville is 3.65 inches. So this three-day period was over twice the average for the entire month. Continue reading

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Year to Date – Cool and Wet in Illinois

It is probably not shocking news to find out that the first 8 months of 2014 have been both cooler and wetter than average for Illinois.

The statewide average temperature for January-August was 50.8 degrees, 3.5 degrees below the 1981-2010 average and tied with 1924 as the fifth coolest on record.

The statewide average precipitation for January – August was 28.79 inches, 1.46 inches above average and the 34th wettest on record.

Here is what the precipitation departures look like through the end of August. Several areas in northeast and east-central Illinois have precipitation departures of 6 to 12 inches above average in the shades of blue, and a few areas with 12 to 16 inches above average. Areas in green are 2 to 6 inches above average. Only a few small areas in tan/beige are 2 to 4 inches below average.


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Summer Weather Gives Way to Fall

If you look at the start to September, temperatures have run 3 degrees above average. And yesterday and today have been the hottest yet with temperatures the 80s and 90s across much of state. But that is about to change as a cold front pushes through later today. This weekend and next week will be cooler with highs in the 70s and low 80s.  I am looking forward to that.

Average daily highs in September in Illinois range from the low to mid 70s in northern Illinois to the low 80s in southern Illinois (map below, click to enlarge).


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Wet August Wraps Up Cool, Wet Summer in Illinois

Highlights: The 12th wettest August in Illinois finishes out the 10th wettest summer on record. While August was slightly warmer than average, the summer was cooler than average. Here are the statistics.

August Statistics

The statewide average precipitation for August was 5.18 inches, 1.59 inches above average and the 12th wettest on record. The wettest area of the state was Cook County. The largest monthly total was from a CoCoRaHS site (IL-CK-100) in Cicero with 10.20 inches of precipitation.

This first map shows several areas across the state with amounts of 7 to 10 inches (oranges and reds), according to radar estimates. There were a few areas in the northwest and east-central Illinois with only 2 to 3 inches. The second map shows the departures from average, showing the many areas with 2 to 8 inches above average for the month.



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Illinois on List Twice for Billion-Dollar Weather Disasters of 2013

According to the National Climatic Data Center, Illinois was on the list twice for billion-dollar weather disasters in 2013. In both cases, some damages occurred elsewhere but Illinois took the brunt of the losses. These numbers are based on reports from government agencies, media reports, and insurance industry estimates.


The first was the flooding in the Chicago area in April 2013. I had posts on this event here, here, and here. This event produced an estimated $1 billion in damages and led to 4 deaths. They described it as:

A slow-moving storm system created rainfall totals of 5 to 10 inches across northern and central Illinois including the Chicago metro. This resulted in damage to many homes and businesses. There was also severe weather damage from wind and hail across Indiana and Missouri.

The second was the November 17, 2013, tornado outbreak that caused an estimated $1 billion in damages and led to 8 deaths. I wrote about it herehere, here, here, and here. They described it as:

Late-season outbreak of tornadoes and severe weather over the Ohio Valley (IL, IN, MO, OH, KY, MI) with 70 confirmed tornadoes. Most severe impacts occurred across Illinois and Indiana.

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