April 4th Wettest On Record


This April was the 4th wettest on record for Illinois with 6.90 inches, based on the preliminary numbers. That was 3.13 inches above the long-term average of 3.77 inches.
To show you how wet it was, this April easily beat out the combined statewide rainfall totals for Illinois in May, June, and July of 2012 during the worst of the drought. The total rainfall for those months in 2012 were 2.50 inches, 1.80 inches, 1.48 inches, respectively, which led to a total of only 5.78 inches. That was 1.12 inches less than this April!
The first map below shows the spectacular rainfall totals across much of the state. The areas in yellow and orange were 6 to 9 inches. A few areas in pink and red were 9 to 11 inches. This product has a 4 kilometer resolution and is based on radar estimates calibrated with rain gauges.
The second map shows the same rainfall amounts expressed as a percentage of the long-term average. There was a small patch of below-average rainfall in far southern Illinois. Otherwise the rainfall across the rest of the state was much above average. Many areas in the dark blue were 2 to 3 times their long-average rainfall.
Speaking of rain gauges, the two largest monthly totals for April so far were Augusta with 12.28 inches and Naperville with 11.03 inches. Several more stations reported totals in the 10-inch range.
There were two major impacts of the wet April. One was widespread flooding on the Illinois, Wabash, and Mississippi Rivers and their tributaries. Several sites along the Illinois reported record high river crests in April. Because the flooding included the Chicago area, the dollar damages and number of people affected will be quite large.
The second impact of the wet April was the delay in fieldwork. In the April 29 USDA NASS report, only 1 percent of the corn crop was planted, compared to 76 percent last April, and a five-year average of 36 percent.


The statewide average temperature was 50.1 degrees and 2.3 degrees below average. That was not record-setting but reflects the fact that we had a lot of cool, cloudy days in April.


The April 2013 precipitation, ending with reports on the morning of May 1. Click to enlarge.
April 2013 precipitation, ending with reports on the morning of May 1. Click to enlarge.

April precipitation, expressed as a percent of the long-term average. Click to enlarge.
April precipitation, expressed as a percent of the long-term average, for reports ending on the morning of May 1. Click to enlarge.

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.