Here are the statewide monthly temperature and precipitation departures for Illinois in 2015. The departures are from the 1981-2010 averages.
The standout features of 2015 so far have been:
- the very cold February, 19.4 degrees, and tied with 2014 as the 8th coldest February on record;
- the very wet June, 9.44 inches of precipitation and the wettest June on record.
Statewide records go back to 1895 and are maintained by the National Centers for Environmental Information.
Temperatures. Click to enlarge.
Between 1 to 3 inches of rain (shades of green and yellow in the map below) has fallen over much of southern and central Illinois in the last 14 days through this morning. Meanwhile, areas generally to the north of Interstate 80 have less than an inch of rain (shades of blue).
Illinois experienced its wettest May – July on record with 19.69 inches of precipitation, 7.88 inches above the 20th century average, according to the National Centers for Environmental Information. Most of that was due to the record precipitation of June with 9.44 inches statewide, based on their latest numbers and discussed in more detail here.
Here is the time series of May – July precipitation in Illinois since 1895. The second wettest May – July was a tie between 1990 and 2010. And it was just three years ago, in 2012, when Illinois had its third driest May – July on record with only 5.60 inches (6.21 inches below the 20th century average).
May-July precipitation in Illinois. Click to enlarge.
Here is what the May – July 2015 precipitation departures from the 20th century average looked like for climate division in Illinois and surrounding states. That is about an extra two months of precipitation during that three-month period.
Click to enlarge.
Illinois has an increased chance of being cooler-than-average for August, according to the NWS Climate Prediction Center. The new forecast was released on July 31, 2015.
One of the major drivers in the forecast is that we are currently in an El Niño event. Historically, August temperatures tended to be cooler than average during El Niño events.
This forecast of a cooler August follows on the heels of our cool July. Besides El Niño, in the past the temperature pattern experienced in July has a tendency to carry over into August. That is a hot July tends to carry over to a hot August and a cool July tends to carry over to a cool August.
This is largely the result of soil moisture status. Dry soils in July (i.e., drought) leads to warmer temperatures in both July and August. On the other hand, wet soils in July hold down August temperatures as more solar radiation goes into evaporating and transpiring water back into the atmosphere and less into heating up the atmosphere.
Click to enlarge.
Based on preliminary data, July was both cooler and wetter than average for Illinois.
The statewide average temperature in July was 74.4 degrees, 0.9 degrees below average. That is not nearly as cool as our record-setting July 2014 when the average temperature was only 70.3 degrees (5.0 degrees below average). On the extreme other end, July 2012 was 81.8 degrees (6.5 degrees above average and the 2nd warmest on record). More on July temperature trends in another post.
July Precipitation. Click to enlarge.
According to the NOAA Storm Prediction Center, Illinois is ranked fourth in the nation for the number of tornado reports in 2015. Here are the top five states:
- Texas with 164 reports
- Kansas with 150 reports
- Oklahoma with 100 reports
- Illinois with 64 reports
- Colorado with 48 reports
April 9, 2015. Click to enlarge.
The most outstanding event for 2015 was the April 9 outbreak that produced 11 tornadoes, including a rare EF-4 tornado. The map on the left shows all the severe weather reports for that day. More on this outbreak can be found here.
The map below is for all the tornado reports across the US in 2015. Many of the Illinois tornadoes occurred in far northern and far southern Illinois this year, while central Illinois has been relatively quiet. Continue reading
Here is the latest radar/raingauge estimated rainfall totals for July across the Midwest through this morning.
Much of the Corn Belt has been extremely wet. Heavy rains amounts of 5 to 10 inches are found across Minnesota, Wisconsin, Missouri, southern Iowa, Illinois, Indiana, Ohio, and Kentucky for July. Even portions of the Plains states received 2 to 5 inches of rain, which is well above their typically dry July.
For Illinois, amounts of 5 to 10 inches are found between East St. Louis, Moline, and eastward, as well as south of Carbondale and parts of northeast Illinois. Most of the rest of the state has received 2 to 5 inches. There are even a few small areas with less than 2 inches of rain in southern Illinois and the northwest corner.
July Rainfall. Click to enlarge. Areas shaded in red and purple have between 5 and 10 inches of rain. Areas in yellow and orange are 2 to 5 inches, and areas in green are less than 2 inches.