Weather Review of 2013 in Illinois

Summary

In Illinois, 2013 was slightly cooler and wetter than average. The first half of the year was the wettest on record, which led to flooding and planting delays across the state. This was followed by a rapid onset of drought in parts of the state in late summer and fall. The year finished on a cold note with below-average temperatures in November and December.

By the Numbers

Based on the latest data, the statewide average temperature for 2013 in Illinois was 50.8 degrees (1.4 degrees below the 1981-2010 average). That is much cooler than 2012 when the statewide average temperature was 55.6 degrees.

The statewide average precipitation for 2013 in Illinois was 43.77 inches (3.58 inches above the 1981-2010 average). The precipitation for the two halves of 2013 were very different. The precipitation for the first 6 months of 2013 totaled 28.96 inches and was 9.13 inches above average and the wettest January-June on record. The precipitation in the following 6 months of 2013 totaled 14.81 inches and was 5.56 inches below average and the 19th driest July-December on record.

By the way, the 2013 annual statewide average precipitation of 43.77 inches was 12.94 inches wetter than 2012 when we received only 30.83 inches across the state.

Annual Precipitation Maps

The annual precipitation for 2013 and its percent of average across the state are shown in the following two maps (click to enlarge). The largest precipitation totals were in the far southern region of the state (greater than 50 inches) and the smallest totals were in parts of central and northwestern Illinois (less than 35 inches). A few of the dry spots were down to 90 percent of the average annual precipitation. While that was modest compared to the drought of 2012, those areas were showing some lingering signs of drought in stream flows, lake levels, and groundwater supplies even in late December.

IL-prcp-mpe-y2d-tot-20131231

IL-prcp-mpe-y2d-pct-20131231

Monthly Temperature and Precipitation

Here is the breakdown of temperatures and precipitation by month for 2013 with comparisons to the 1981-2010 average. As the first graph and table show, January was warmer than average, while March was much colder an average due to the late start and ending of “winter”. In fact, winter weather didn’t arrive until late February and lingered on into early April. Summer temperatures was slightly cooler than average as the growing season finished off with a warmer than average September. November and December were noteworthy for being exceptionally cold and combined they were the 8th coldest November and December on record.

As mentioned earlier, the precipitation for 2013 was memorable for the wet spring and early summer, followed by dry weather starting in July. The heart of the wet weather was in April, May, and June. This was followed by three months of significant dryness (July-September). The second graph and table shows the month by month precipitation.

Note: here the statistics for 2013 are compared to the 30-year average, or normal, for 1981-2010.  

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Temperature (F)
Year Month Temp Normal Depart
2013 Jan 28.9 24.6 4.3
2013 Feb 29.9 30.1 -0.2
2013 Mar 34.1 40.7 -6.6
2013 Apr 49.7 51.7 -2.0
2013 May 63.6 62.4 1.2
2013 Jun 71.3 71.6 -0.3
2013 Jul 72.9 75.4 -2.5
2013 Aug 72.3 73.2 -0.9
2013 Sep 68.4 65.8 2.6
2013 Oct 54.3 54.1 0.2
2013 Nov 38.3 41.5 -3.2
2013 Dec 25.5 29.9 -4.4
Precipitation  (inches)
Year Month Prcp Normal Depart
2013 Jan 3.87 2.12 1.75
2013 Feb 2.82 2.11 0.71
2013 Mar 2.74 2.98 -0.24
2013 Apr 7.10 3.80 3.30
2013 May 7.02 4.62 2.40
2013 Jun 5.41 4.20 1.21
2013 Jul 3.14 4.05 -0.91
2013 Aug 1.63 3.60 -1.97
2013 Sep 1.73 3.24 -1.51
2013 Oct 3.14 3.26 -0.12
2013 Nov 2.68 3.47 -0.79
2013 Dec 2.50 2.74 -0.24
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One thought on “Weather Review of 2013 in Illinois

  1. […] At the state level, Illinois had an average temperature of 50.8°.  That was quite a bit cooler than the statewide average of 55.6° in 2012.  Only four months (see image above) saw above average temperatures last year. […]

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