Second Coldest April on Record in Illinois

Temperature

Based on the official data, the statewide average temperature was  44.5 degrees,  8.1 degrees below normal. It was the second coldest April on record, only beaten by 43.1 degrees set in April 1907. Our statewide records go back to 1895. Normal refers to a specific benchmark, the 1981-2010 average. See the longer explanation here.

Here are the temperature departures from normal look like across the Midwest. Areas in green are 1 to 9 degrees below normal, while areas in icy blue are 9 or more degrees below normal. The lowest temperature reported in Illinois for April was -1 at both Avon and Lincoln on April 2. At the other extreme, we did reach into the 80s at times during the month. The warmest reading was 86 degrees at Kaskaskia on April 13.

map1

Precipitation Continue reading

April Temperatures in Illinois Warm Over the Last Century

According to the National Centers for Environmental Information (NCEI), the average April temperature in Illinois has warmed by 2 degrees over the last century. In addition, the most recent decade of 2006-2015 was the warmest set of Aprils on record. Statewide records go back to 1895.

Here are the statewide average temperatures for April in Illinois plotted by year. The purple line and black dots show the year-to-year variability in April temperatures in Illinois. The blue line shows the upward trend. You can find the original data and graph here.

ts1

Continue reading

Above-Average Temperatures for April in Illinois

While there were a few cold stretches in April, the statewide average temperature for the month was 54.1 degrees, 1.7 degrees above average.

Precipitation in Illinois for April was more complicated. April precipitation was in the range of two to four inches in northern and central Illinois, and 4 to 7 inches in southern Illinois. As a result, the northern two-thirds of the state was slightly below average while the southern third was up to 2 inches above average. Fort Massac State Park reported the highest monthly precipitation total of 7.80 inches.

prcpmo1
April Precipitation. Click to enlarge.
prcpmo2
April Precipitation Departure. Click to enlarge.

Continue reading

April 4th Wettest On Record

Precipitation

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.

Temperature

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.

Figures

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.

April Already 4th Wettest on Record

Based on preliminary data, this April in Illinois is already the 4th wettest on record with 6.58 inches of precipitation. Average statewide precipitation for April is 3.77 inches. So we are already almost two inches above average.

According to the NWS forecast, more rain is expected across southern Illinois on Friday and Saturday. Therefore, it is possible that we will move up the list by the end of the month. In addition, some sites may have already reached their record for April, including the city of Chicago.

Top 5 Wettest Aprils

  1. 2011 with 7.40 inches
  2. 1957 with 7.13 inches
  3. 1927 with 6.95 inches
  4. 2013 with 6.58 inches
  5. 1944 with 6.50 inches

Precipitation Pattern Across the State

Here is how the precipitation has been distributed around the state, based on our multi-sensor precipitation product, with the actual amounts and the departures from average. Many parts of central and northern Illinois have more than double their average April precipitation (shades of purple in the second map).

April precipitation in inches for the first 24 days of the month. Click to enlarge.
April precipitation in inches for the first 24 days of the month. Click to enlarge.
April precipitation as departures from average. Click to enlarge.
April precipitation as departures from average. Click to enlarge.

Ten Coldest March’s and What Follows

As previously reported, based on preliminary data this March in Illinois was 34.1 degrees and the 11th coldest March on record. What were the ten coldest March’s on record? I have listed them in the table below. Also I looked to see what happened in April after these chilly March’s. It turns out that half are above average and half are below average – a virtual coin toss.

The columns labeled “Depart” are the departures from the 1981-2010 statewide averages. Probably the biggest turnaround was between March 1960, which was the coldest March on record and 15.5 degrees below average, compared to April 1960 which was 2.2 degrees above average. The statewide temperature records go back to 1895. 

Rank Year March Depart April Depart
1 1960 25.6 -15.5 54.6 2.2
2 1906 30.3 -10.8 54.5 2.1
3 1912 30.4 -10.7 52.6 0.2
4 1965 31.1 -10.0 52.9 0.5
5 1984 33.0 -8.1 49.8 -2.6
6 1932 33.2 -7.9 52.1 -0.3
7 1978 33.5 -7.6 52.5 0.1
8 1989 33.5 -7.6 51.1 -1.3
9 1947 33.8 -7.3 51.0 -1.4
10 1926 34.0 -7.1 45.4 -7.0
11 2013 34.1 -7.0 ?? ??

BTW, so far this April has been cool. The first 7 days averaged 44.4 degrees statewide, and about 3 degrees below average.

April Colder Than March – A Rare Case

Temperature

The statewide average temperature for April 2012 was 54.1 degrees, based on available data. The statewide average temperature for March was 55.0 degrees, based on the latest numbers from NOAA.  That means that April was almost a degree cooler than March. What makes this even more impressive was that the April temperatures are still 2.4 degrees above normal!

By the way, the statewide normal monthly temperature is 40.7 degrees for March and 51.7 degrees for April, an eleven degree rise.

How rare is it for April to be colder than March? In the statewide records that extend back to 1895, it happened only in 1907 when the March temperature was 47.0 degrees and the April temperature was 43.2 degrees. In all the other cases between 1895 to 2011, April was always warmer.

The highest temperature reported in the state for April was 92 degrees at Kaskaskia on April 2 and at Jacksonville and Pana on April 3. The coldest temperature reported was 23 degrees at Jerseyville on April 17.

Precipitation

The statewide average precipitation was 3.32 inches. That is about 0.5 inches below normal. The rainfall over the weekend was fairly widespread and helped much of the state. In general, the heaviest rains of 5 inches or more fell east of St. Louis. Meanwhile, rainfall amounts of 2 inches or less fell in far southern Illinois, far northwestern Illinois, and a large swath between Peoria and Kankakee. Those areas were 1 to 3 inches below normal for the month (second map).

The highest monthly rainfall total reported in Illinois for April was a CoCoRaHS observer near Belleville (IL-SC-3) with 8.64 inches. Some of the lowest monthly rainfall totals in the state were in Kankakee and Will Counties. For example, Grant Park (IL-KK-19) in Kankakee County reported all 30 days and only received 0.83 inches for the month.

April rainfall totals, based on a radar product developed by the National Weather Service. Click to enlarge.
April rainfall departure from normal, based on a radar products developed by the National Weather Service. Click to enlarge.