July – Warmer and Wetter than Normal

The average temperature for July in Illinois was 77.7 degrees, 1.9 degrees above normal. That’s warm but not record-breaking by any means. By contrast, the average temperature of last July was 70.2 degrees. Not only was this year warmer but it was considerably more humid as well.

The average rainfall for July in Illinois was 5.6 inches, 1.8 inches above normal. BTW, the wettest July on record was 1958 with 8.03 inches.

The largest rainfall totals occurred in western and far northern Illinois as well as an area along I-70. Amounts of 8 to 12 inches were common in these areas.

Southern Illinois was much drier in July with amounts of only 1 to 3 inches in many locations. In fact, the US Drought Monitor categorized southern Illinois as being “abnormally dry” by. Another area of dryness is through central Illinois in an area bound by Moline, Kankakee, Danville, Springfield, and Peoria.

Rainfall Totals for July in the Chicago Area

Here are some rainfall totals for July 2010 [updated on August 3] for the Chicago area. This is preliminary and may contain missing or incorrect data. Missing data can make the monthly totals too low.  Based on what has been reported so far, Midway Airport has set a new record for July precipitation, beating the old record of 8.98 inches set in 1957.

Monthly Data for July 2010 for Illinois – Northeast Climate Division
Station Total Precipitation
BARRINGTON 3 SW 7.18
BELVIDERE 7.24
CHICAGO BOTANICAL GARDEN 5.51
CHICAGO MIDWAY AP 10.39
CHICAGO MIDWAY AP 3 SW 9.17
CHICAGO OHARE INTL AP 8.84
DE KALB 6.92
EARLVILLE 3 S 3.31
ELBURN 6.28
ELGIN 7.68
GENOA 2 SW 8.89
GLEN ELLYN 4 S 7.48
HARVARD 9.52
JOLIET BRANDON RD DM 5.00
MARENGO 6.53
MARSEILLES LOCK 3.87
MCHENRY STRATTON L 3.28
MENDOTA 2 SE 3.29
MONEE RSVR 6.01
MORRIS 3.89
MUNDELEIN 4 WSW 7.06
NEWARK 2 SSE 3.91
OAK BROOK 2W 9.02
PARK FOREST 6.38
PERU 2.74
PLAINFIELD 3 NE 7.48
ROMEOVILLE LEWIS UNIV AP 8.05
SHABBONA 3S 5.29
SPRING GROVE 6.89
ST CHARLES 7 NW 9.44
STREAMWOOD 6.91
WHEATON 3 SE 6.25
WOODSTOCK 5 NW 6.65
YORKVILLE 3 SW 4.31

Warmer and Mostly Wetter July (so far)

The statewide average temperature for July 1-22, 2010, in Illinois is 77.2 degrees, 1.1 degrees above normal for this time period. The state average precipitation for the same period is 3.46 inches, 0.70 inches above normal.

Northern and eastern Illinois are a little drier on average. However, even those drier areas contain locations with very impressive rainfall amounts.

Midwest Rainfall
Midwestern rainfall for the period July 1-21, 2010. Map courtesy of NOAA's Midwestern Regional Climate Center.

Table 1. Temperature and precipitation amounts and departures from normal by climate division in Illinois for July 1-22, 2010. A map of the climate divisions can be seen below the table.

Climate Division Temperature (F) Depart (F) Rainfall (in) Depart (in)
Northwest 75.2 1.2 1.96 -0.86
Northeast 76.2 2.3 1.44 -1.41
West 76.9 0.4 6.54 3.58
Central 76.7 1.1 2.85 0.04
East 76.2 1.2 2.08 -0.88
South Southwest 77.5 0.4 5.05 -0.88
South Southeast 78.0 0.9 5.10 2.25
Southwest 79.3 1.0 2.89 0.39
Southeast 79.3 1.0 2.90 0.39
State 77.2 1.1 3.46 0.70
Illinois Climate Divisions
Illinois Climate Divisions (coincides with crop reporting districts as well).