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).

Now 4th Wettest June on Record in Illinois

Right now the statewide precipitation average of 7.20 inches makes this the 4th wettest June on record. Statewide records go back to 1895. Here are the top 5 …

  1. 8.37 inches in 1902
  2. 7.68 inches in 1998
  3. 7.31 inches in 1928
  4. 7.20 inches in 2010 (as of June 25)
  5. 7.13 inches in 2000

With rain in the NWS forecast for the weekend, it is possible to move up to third or perhaps even second place. However, it would take widespread heavy rains to beat 1902. By the way, normal statewide June rainfall is 4.1 inches.
Of the ten wettest Junes, in 7 out of 10 cases rainfall returned to within an inch of normal conditions in July and August. Only in 1993 did the wet conditions persist into July and August. Only in 1945 and 1947 did we experience much drier conditions in July and August.
Meanwhile temperatures have been above normal for June so far. The statewide average temperature of 74.9 degrees is 3.6 degrees above normal. This is now the tenth warmest June on record (as of June 25). The warmest June on record for Illinois is 1934 with 78.5 degrees. The only recent year in the top 10 list is 2005 with 74.8 degrees.

Rains and Hot Weather Continue in Illinois

The wetter and warmer than normal weather continued in Illinois this week. For the period of June 16-22, the state average temperature was 76.8 degrees, 3.6 degrees above normal. Meanwhile the statewide average precipitation was 2.46 inches, 1.55 inches above normal.
Illinois already experienced above normal temperature and precipitation in the first half of June. Combined with this week’s weather, the statewide average temperature for June so far is 74.5 degrees, 3.4 degrees above normal. The statewide average precipitation at this point is 6.35 inches, 3.37 inches above normal.
If you are thinking that we must be closing in on a record, you are correct. Statewide this is already the 10th wettest June on record. The wettest June on record is 1902 with 8.37 inches. Several individual station records will be set as well. For example, Galesburg has already received 11.25 inches this month. This handily beat the old June record of 9.97 inches set in 1974. This is impressive given that their records go back to 1927.
The wettest areas of the state are western Illinois and east-central Illinois. Based on radar estimates and reports from weather observers, monthly totals of 9 inches or more were common in these areas. The wettest spot so far is Warsaw (Hancock County CoCoRaHS observer) which has reported 11.38 inches through today (June 22) with more rain falling after the regular reporting time.
Here are the precipitation and precipitation departure maps for June 1-22, 2010, for Illinois.

June 1-22, 2010 rainfall in Illinois
The June 1-22, 2010, rainfall in Illinois. Map courtesy of the NOAA Midwestern Regional Climate Center.

June 1-22, 2010 rainfall departure for Illinois
The June 1-22, 2010, rainfall departures from normal in Illinois. Map courtesy of the NOAA Midwestern Regional Climate Center.

Fourth Warmest Spring in Illinois

Based on preliminary data, the statewide average temperature for spring in Illinois was 55.3 degrees, 3.3 degrees above normal and the fourth warmest spring on record. Warmer than normal conditions prevailed in the spring months of March (+2.5 degrees), April (+6.2 degrees), and May (+1.3 degrees).
The statewide average precipitation for spring was 11.97 inches, just 0.7 inches above normal. This is notably less than the 15.83 inches that fell in the spring of 2009 and the 14.21 inches that fell in the spring of 2008.
Climatologists and meteorologists tend to use the calendar months of March-May to define spring and not the astronomical definition from the vernal equinox (usually March 20) to the summer solstice (usually June 21). The calendar months better match the climate of Illinois. Our winter weather usually diminishes by early to mid March across much of Illinois and summer weather usually arrives long before June 21.

Spring temperatures in Midwest.
Spring temperature departures for the Midwest for 2010.

Spring precipitation in the Midwest
Spring precipitation in the Midwest for 2010.