October Wetter Than Average for Illinois

Based on preliminary numbers*, the statewide average precipitation for October in Illinois was 4.5 inches, which is 1.2 inches above average. It was the 15th wettest October since 1895. The wettest October on record for the state was 1941 with 9.06 inches of precipitation.

The largest precipitation totals were in the central third of the state where 6 to 8 inches were common. Greenfield had an incredible 9.94 inches of precipitation. Medora, Girard, and Carlinville also reported over 9 inches of precipitation. Precipitation totals were more moderate elsewhere; 4 to 6 inches in southern Illinois and 2 to 4 inches in northern Illinois. Also, several locations in northeast Illinois reported seeing traces of snow for the month.

The statewide average temperature was 54.0 degrees, 0.1 degrees below average.

*I updated these numbers on November 2 with only a 0.2 degree change in temperature from 54.2 to 54.0 degrees.




The plot of past October precipitation for Illinois (below) shows that things have become slightly wetter over time, about 0.64 inches in the last century. The outstanding October’s of 1941 and 2009 are easily seen as well.


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.


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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Agricultural Disaster Declaration for Illinois

Governor Quinn announced yesterday that federal disaster assistance is available to help Illinois farmers who suffered crop losses due to flooding this year (full press release).

As noted in the press release, the January-June period was the 4th wettest on record (27.2 inches, 8 inches above average) and an April that was the wettest on record with 7.59 inches.

I have generated a file with the monthly precipitation for 2011 for all available NWS cooperative observer sites in Illinois. The new 1981-2010 monthly precipitation normals for Illinois are posted as well. Additional precipitation data can be found at cocorahs.org using their precipitation summary product. It works best if you select your county and not the state. 

January-June 2011 precipitation
January-June 2011 precipitation for Illinois. The heaviest totals were in southern Illinois. Click to enlarge.















January-June 2011 precipitation departure
January-June 2011 precipitation departure from average for Illinois. Areas in blue had precipitation that was at least 12 inches above average. Click to enlarge.

Wet Year So Far in Illinois

The statewide precipitation for June is 6.6 inches, 2.5 inches above the 1971-2000 average (normal). That makes it the ninth wettest June on record (based on preliminary numbers as of June 28, 2011).

The statewide precipitation for the first six months of 2011 is 27.2 inches, 7.7 inches above the 1971-2000 average. That makes it the fourth wettest January-June on record. Statewide records go back to 1895.

The figure below shows the June departure from normal precipitation across the US. Cool coolers (green, blue, purple) show abnormally wet conditions. Warm colors show abnormally dry conditions. Wet conditions have prevailed from Montana, into the Dakotas, Nebraska, Iowa, northeastern Missouri, across Illinois, and much of the lower Ohio River valley. However, dry conditions are not far from Illinois borders, especially to our southwest.

June rainfall across the US (courtesy NOAA).
June departure from normal precipitation across the US (source NOAA). Click to enlarge.

The figure below shows the year-to-date departure from normal precipitation across the US. Like June, the band of above-normal precipitation extends from Montana, down the Missouri River, and up the Ohio River valleys. This area has seen abundant atmospheric moisture and a strong, persistent jet stream for much of winter and spring. Meanwhile, the Southwest and South have struggled with dry conditions. BTW, it is not unusual to have one part of the US experiencing drought while another part experiences heavy rains and flooding. It is amazing that you can go from southern Illinois with its 8 to 16 inches of above normal precipitation to Arkansas and Mississippi and find areas that are 8 to 16 inches below normal on precipitation.

Year to date precipitation departure for the US.
Year to date departure from normal precipitation across the US (source NOAA). Click to enlarge.

Revised Winter Forecast

NOAA’s Climate Prediction Center has revised their winter forecast today. Their earlier outlook for December-February called for increased chances of above normal temperatures in the southern two-thirds of Illinois and above normal precipitation for all of Illinois.

However, December is already shaping up to be on the cold and dry side (see earlier post).

Now their outlook for January calls for equal chances of above, below, and near-normal temperature and precipitation in Illinois. It’s what I call a neutral forecast.

In their forecast for January-March, they call for an increased chance of above-normal precipitation in Illinois as well as much of the Ohio River Valley and Great Lakes region (see map below). Their temperature outlook remains neutral for Illinois for this period.

NOAA precipitation outlook for January-March
NOAA's Climate Prediction Center precipitation outlook for January-March.

Updated Forecast for December and Winter

NOAA’s Climate Prediction Center has come out with a new forecast for December and for December-February (winter). This is part of their routine update cycle.


The outlook for December in Illinois calls for an increased chance of above normal temperatures.  An increased chance of above normal temperatures translates into just a few degrees above normal. Temperatures in Illinois have run an average of 2.9 degrees above normal for every month since March of this year. Therefore, continuing with a forecast for above-normal temperatures is not surprising.

The outlook calls for equal chances of above, below, or near-normal precipitation (or equal chances as they call it) in December in Illinois.

December-February (winter)

The outlook for December-February remains the same as last month. There is an increased chance of above-normal precipitation for all of Illinois. And, there is an increased chance of above-normal temperatures for the southern two-thirds of the state. See the figure below for more details.

CPC forecast
NOAA's Climate Prediction Center forecast for December and December-February (click to enlarge).