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:
8.37 inches in 1902
7.68 inches in 1998
7.67 inches in 2010
7.31 inches in 1928
7.13 inches in 2000
6.99 inches in 1924
6.89 inches in 1993
6.80 inches in 1945
6.73 inches in 2011
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.
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.
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.
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.
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.