Ninth Wettest June on Record for Illinois

The statewide average precipitation for June in Illinois was 6.7 inches. That’s 2.6 inches above the 1971-2000 average. Rainfall totals at individual sites were impressive. The highest rainfall total for June was from a CoCoRaHS observer near Warsaw (Henderson County) who reported 20.85 inches. NWS cooperative observers in Loami reported 14.48 inches and in Jacksonville reported 13.74 inches

The statewide average temperature for June was 72.8 degrees, 0.9 degrees above average. The warmest reported temperature for the month was 100 degrees in DuQuoin on June 4.

If it feels like we are seeing a lot of wet Junes, you are right. First is a list of the top ten wettest Junes in Illinois:

  1. 8.37 inches in 1902
  2. 7.68 inches in 1998
  3. 7.67 inches in 2010
  4. 7.31 inches in 1928
  5. 7.13 inches in 2000
  6. 6.99 inches in 1924
  7. 6.89 inches in 1993
  8. 6.80 inches in 1945
  9. 6.73 inches in 2011
  10. 6.52 inches in 1957
We also have a five-year streak of above-average precipitation for June in Illinois:
  • 2007: 4.18 inches, 0.06 inches above average
  • 2008: 5.74 inches, 1.62 inches above average
  • 2009: 5.20 inches, 1.08 inches above average
  • 2010: 7.67 inches, 3.53 inches above average
  • 2011: 6.73 inches, 2.61 inches above average
We don’t know what will happen in July. However, the last three years have ended up with wetter than average July’s, on a statewide basis.

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.

Severe Weather in Illinois in 2011

According to preliminary data from the NOAA Storm Prediction Center (SPC), in 2011 Illinois has received:

  • 55 reports of tornadoes
  • 247 reports of hail greater than 1 inch in diameter
  • 474 reports of wind damage

So it has been a fairly active year for severe weather in Illinois. Fortunately, we have not experienced the level of devastation as was seen in the Southeast or in Joplin, MO.

Personally, the outstanding feature of this year is hail. I’ve had pea-sized hail at my house four times this year (including last night at around 1 am). That’s unusual for me because I’ve gone for years at a time without seeing any hail at home. Out of curiosity, I pulled up the hail statistics since 2000 for Illinois from the SPC site. Beginning in 2011, they changed the significant hail criteria from three-quarter inch to one inch so any hail report less than one inch will no longer be counted.

  • 247 in 2011, as of June 27, 2011
  • 120 in 2010
  • 245 in 2009
  • 502 in 2008
  • 252 in 2007
  • 906 in 2006 (also a big year for tornadoes)
  • 339 in 2005
  • 383 in 2004
  • 588 in 2003
  • 256 in 2002
  • 193 in 2001
  • 342 in 2000

Forecast for This Summer in Illinois

The Climate Prediction Center (NOAA) just released their outlook for July as well as July-August-September. In their own words, Illinois has equal chances (EC) of above-, below-, or near-average temperatures and precipitation for this summer. It’s what I would call a “neutral forecast” for us.

On the other hand, the Northern Plains are expected to be cooler and wetter than average for both July and July-September. Meanwhile, much of the South is expected to be warmer than average this summer.

One factor that will not dominate this summer is La Nina. Sea surface temperatures in the Pacific along the equator have returned to neutral conditions and will remain so at least through this summer.

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The July and July-September outlooks from the Climate Prediction Center, NOAA. Click to enlarge.

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


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!


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).