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.
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.
Here are the June 2010 rainfall totals for sites in Illinois, ranked from highest to lowest. The numbers are impressive with 35 sites scattered throughout northern and central Illinois reporting 10 or more inches of rain.
These numbers are preliminary and have not been quality-controlled. In some cases data may be missing that could lead to totals that are too low. Due to the localized nature of some of the heavier storms, one may see large differences over short distances. These sites are part of the NWS cooperative observer program – volunteers with standard equipment and observing practices.
Illinois has experienced the 2nd wettest June on record, based on preliminary records through June 30. The statewide average rainfall was 7.8 inches, 3.7 inches above normal. The wettest June on record was 1902 with 8.37 inches. The rains over the weekend, especially north of I-80 and along I-70 caused this June to move up from fourth to second wettest June on record. Statewide records extend back to 1895. This number is provisional and may change slightly as more data comes in.
The larger rainfall totals occurred in the northern two-thirds of the state where amounts of 7 to 12 inches were common. Meanwhile far southern Illinois remains closer to normal with amounts ranging from 3 to 6 inches.
NOAA has an excellent website for monitoring global and U.S. conditions at http://www.ncdc.noaa.gov/climate-monitoring/index.php This site gives an overview of temperatures, precipitation, global hazards, tornadoes, wildfires, droughts, and other conditions for each month. The monthly reports are typically posted about a week or so after the end of the month. You can choose from the archive of past months/years as well.
Here is a screen shot of one of the many products available. This one is called the “U.S. Climate at a Glance” product. With this particular product you can generate national, regional, statewide maps as well as plots for key cities. Give it a try.