June Is Wet and Warm, So Far

Based on preliminary data, the average temperature for Illinois in the first half of June is 73.2 degrees, 2.9 degrees above average. The statewide average precipitation was 3.32 inches, 1.13 inches above average.
Table 1 shows the temperatures and precipitation for June by climate division, also known as crop reporting districts. Much of Illinois has been wet, but far southern Illinois has been on the dry side in the last few weeks. Not that it’s necessarily a problem since that area had exceptional rainfall totals in both April and May.
Table 2 shows the same thing, only for the year to date. Overall, Illinois temperatures in 2011 are about 1 degree below average while precipitation is 6.42 inches above average. The precipitation departures are most impressive in southern Illinois and exceed 10 inches in those areas.

Table 1. Illinois conditions for June 1-16, 2011.

Climate          <------Temperature----->   <---------Precipitation--------->
Division         Actual   Normal      Dev   Actual   Normal     Dev   Percent
-----------------------------------------------------------------------------
Northwest          69.6     68.1      1.4     3.39     2.32     1.08      147
Northeast          68.8     67.5      1.3     3.62     2.26     1.36      160
West               72.3     70.3      2.0     5.86     2.17     3.68      269
Central            71.7     70.0      1.7     3.34     2.08     1.25      160
East               72.0     69.9      2.1     3.13     2.17     0.96      144
West-southwest     74.6     71.1      3.4     4.17     2.05     2.13      204
East-southeast     75.3     71.4      3.9     2.77     2.22     0.55      125
Southwest          77.8     72.1      5.7     1.35     2.16    -0.81       63
Southeast          78.0     72.5      5.5     1.74     2.27    -0.53       77
State              73.2     70.2      2.9     3.32     2.19     1.13      152

Table 2. Illinois conditions for January 1 – June 16, 2011.

Climate          <------Temperature----->   <---------Precipitation--------->
Division         Actual   Normal      Dev   Actual   Normal     Dev   Percent
-----------------------------------------------------------------------------
Northwest          39.5     41.4     -1.8    19.64    15.32     4.32      128
Northeast          40.0     41.5     -1.5    21.44    15.58     5.87      138
West               43.1     44.7     -1.5    21.44    16.30     5.14      132
Central            42.7     44.1     -1.4    20.70    16.16     4.54      128
East               42.9     43.9     -1.0    21.98    16.30     5.68      135
West-southwest     45.4     46.5     -1.1    21.92    17.19     4.73      127
East-southeast     46.5     47.0     -0.5    26.56    18.77     7.79      142
Southwest          48.9     49.0     -0.1    30.20    19.93    10.27      152
Southeast          49.6     49.3      0.3    33.15    21.75    11.40      152
State              44.1     45.1     -1.0    23.74    17.32     6.42      137
Dev means Deviation From Normal, Percent means Percent of Normal

Seventh Wettest Spring on Record for Illinois

The statewide average rainfall of 5.6 inches in May, combined with the 2.8 inches in March and 7.3 inches in April, resulted in a total rainfall for this spring at 15.7 inches. That makes it the seventh wettest spring on record since 1895 and 4.3 inches above average.
The heaviest spring rains fell in southern Illinois. Cairo reported the highest total rainfall with 30.90 inches, followed by Brookport Dam with 29.19 inches, Du Quoin with 28.95 inches, and Carbondale with 27.59 inches. These numbers are slightly more than double the average spring rainfall totals.
[update June 7] I just found a CoCoRaHS observer near Anna (IL-UN-3) who reported 37.5 inches of rain during those three months. To put that in perspective, the average ANNUAL precipitation for the Anna area is 48 inches.
The statewide average temperature for this spring was 52.0 degrees, which is right on the 1971-2000 average of 52.0 degrees.
Note about “spring”: in climatology, we define spring as March – May. This definition lines up better with our ideas of spring weather than the astronomical definition of March 20 (equinox) to June 21 (solstice). In much of Illinois, spring weather starts to arrive before March 20 and summer weather starts to arrive before June 21.

Total rainfall for March-May, 2011, in Illinois.
Total rainfall for March-May, 2011, in Illinois. Click to enlarge.

Rainfall departure for March-May, 2011, in Illinois.
Rainfall departures for March - May 2011, in Illinois. Click to enlarge.

May in Illinois – Above Average Rainfall

Precipitation

It should come as no surprise that the May 2011 statewide average rainfall was 5.60 inches, and 1.34 inches above the 1971-2000 average. In the first half of May, the rainfall distribution was lopsided with southern Illinois getting 3-5 inches of rain while much of the rest of the state had less than 2 inches. But the rest of the state caught up in the second half of the month.
For May, the two sites with the heaviest rainfall totals in the NWS cooperative observer network were near the Quad Cities: Woodhull with 9.92 inches and Altona with 9.28 inches. From the CoCoRaHS network, the two sites with the heaviest rainfall totals were on opposite ends of  the state: Anna with 10.04 inches and Algonquin with 9.12 inches.
Here is an amazing thing about the statewide May rainfall – they are almost the same in the last four years:

  • 2011 – 5.60 inches
  • 2010 – 5.59 inches
  • 2009 – 5.65 inches
  • 2008 – 5.39 inches
That’s a spread of only 0.26 inches in four years!

Temperature

The statewide average temperature for May was 62.1 degrees, 0.8 degrees below average. Temperatures ranged from a high of 95 degrees in Prairie City, Fisher, Little Red School House (Willow Springs), Princeville, and Trimble to a low of 24 in Elizabeth.
May 2011 rainfall in Illinois.
May 2011 rainfall in Illinois (click to enlarge).