Another Very Weather-Active July in the Books – Illinois State Climatologist

The preliminary statewide average July temperature was 73.8 degrees, 1.6 degrees below the 1991-2020 average and tied for 29^th warmest on record going back to 1895. The preliminary statewide total July precipitation was 7.01 inches, 2.95 inches above the 1991-2020 average and the third wettest on record.

Data are provisional and may change slightly over time.

Persistently Mild July Temperatures

July gave us a mixed bag of temperatures, but more days last month were cooler than normal. Daily temperatures from Springfield in Figure 1 show temperatures in the third week of the month were consistently 3 to 10 degrees below normal. While last month also brought some intense heat, it was fleeting.

**Figure 1**. Daily July average temperature departures in Springfield.

July average temperatures ranged from the low 70s in northern Illinois to the high 70s in southern Illinois, between 1 and 2 degrees below normal for most of the state (Figure 2). Persistent northwest flow over the big ridge out west helped keep weather cooler and less humid for much of the month. Impressively cool July nighttime lows included 47 degrees in Taylorville and in Joliet. The coolest place in the state last month was Stockton in Jo Daviess County with an average temperature of 69.8 degrees, and the warmest place in the state in July was Carbondale with an average temperature of 77.0 degrees.

**Figure 2**. Maps of (left) July average temperature and (right) July average temperature departures from normal.

Overall, the preliminary statewide average July temperature was 73.8 degrees, 1.6 degrees below the 1991-2020 average and tied for 29^th warmest on record going back to 1895. The preliminary statewide total July precipitation was 7.01 inches, 2.95 inches above the 1991-2020 average and the 3^rd wettest on record. This was also the second consecutive July with a statewide average temperature below normal, the first time we have had back-to-back cooler than normal Julys since 2014-15.

A Hurricane and a Derecho Make for a Very Wet Month

Illinois was starting to get a little dry after a drier than normal June. In fact, over half the state was considered abnormally dry in the U.S. Drought Monitor on July 2. The remnants of one of the strongest early season Atlantic hurricanes on record, Beryl, bent up through the Midwest, producing significant rainfall over a 48-hour period across parts of central and east-central Illinois (Figure 3). Parts of Champaign and Douglas counties picked up more than 4 inches in two days from Beryl, dramatically improving soil moisture and streamflow.

**Figure 3**. Map of 48-hour estimated rainfall totals between July 9 and 10. Source: https://www.weather.gov/ilx/09jul2024-beryl.

Less than a week later, an intense storm system moved across the northern half of the state, producing very heavy rainfall and a derecho that brought severe straight-line winds. Most of the state picked up at least 1 inch of rain over the 48-hour period between July 14 and 16, and multiple spots had over 6 inches, including just over 8 inches in Fulton County (Figure 4). Heavy rain in St. Clair and Washington counties caused significant flooding and forced the opening of a dam spillway near Nashville.

Map of 3-day precipitation totals between July 14th and 16th.

While Illinois’ weather calmed down a bit in the last two weeks of the month, most of the state stayed in an active, stormy pattern. Total July precipitation ranged from around 4 inches in parts of northeast Illinois to over 12 inches in south-central Illinois, between 1 and 7 inches above normal. Several spots in the St. Louis Metro East area picked up more than 13 inches of rain in July, including an incredible 16 inches in Mascoutah. In fact, last month was the wettest July on record in St. Clair County, likely surpassing the previous record by more than 5 inches.

**Figure 5**. Maps of (left) July total precipitation and (right) July precipitation departures from normal.

The preliminary statewide total July precipitation was 7.01 inches, 2.95 inches above the 1991-2020 average and the third wettest on record.

Tornadoes by the Dozen

The same storm system on July 15 produced dozens of tornadoes across Illinois, including more than 30 in the Chicago National Weather Service County Warning Area (Figure 6). It was the largest single-day tornado outbreak on record for the Chicago area.

**Figure 6**. Tornadoes confirmed by the Chicago National Weather Service from July 15 storms.

As of July 31, Illinois had an unofficial total of 126 in 2024 according to the National Weather Service. Importantly, this is a preliminary total and may be adjusted later this year as reports are refined. However, if that total is accurate, it would give this year the highest tornado frequency on record for any. The current official annual tornado record for Illinois is 124 in 2006.

Outlooks

August is the beginning of the end of summer but can certainly bring its fair share of heat. August is also an important month for finishing crops as we move toward fall. The most recent Climate Prediction Center outlooks for August show equal chances of above and below normal temperatures in northern Illinois and higher chances of above normal temperatures in southern and central Illinois. August precipitation outlooks are leaning wetter than normal in northern Illinois and near normal for central and southern Illinois (Figure 7).

The newest climatological fall (September through November) outlooks show slightly higher chances of above normal temperatures, with equal chances of a drier or wetter than normal fall (Figure 7). Either way, many local Illinois orchards have apples ready and that is worth celebrating!