The statewide average temperature for July was 70.3 degrees in Illinois, which ties the record cool July of 70.3 degrees set back in 2009 and 5 degrees below average.
Below is the plot of July temperatures for Illinois since 1895. The green dots are the actual temperature for each year, while the red and blue shading indicate periods of warmer or cooler temperatures. July 1936 (82.8 degrees) is the warmest July on record, followed closely by July 2012 (81.8 degrees). In the bottom right hand corner, are July 2009 and 2014. So in six years, we have experienced the 2nd warmest and twice the coldest July on record.
As this plot indicates, the observed range in July monthly temperatures in Illinois is 12.5 degrees. On another note, the July 2014 average temperature is based on preliminary data so it is very likely that we will break the tie with 2009 as more data arrives.
Of course, the cool weather was not just for Illinois. The map below shows a large area of blue across Illinois and the central US, indicating temperature departures in the range of 4 to 8 degrees below average. And most of the US to the east of the Rocky Mountains experienced below average temperatures for July. Meanwhile, the west and, in particular, the northwest US were exceptionally warm.
The statewide average precipitation was 3.4 inches, which is 0.65 inches below average. The first two weeks of July were exceptionally wet for most of the state, while the rest of the month was dry. In the map below of precipitation departures from average for July, dry conditions prevailed from St. Louis and eastward across Illinois. The wet June and cool July temperatures did help moderate the impact of this dry weather so far.
The latest forecasts from the NWS indicate that cooler and wetter than average conditions will prevail over the next two weeks.