The NOAA Climate Prediction Center has updated their forecast for August. It’s not good news for Illinois with an increased risk of above-normal temperatures and below-normal precipitation.
August – Drought in Central Illinois
The statewide average precipitation was 2.06 inches, 1.6 inches below average and 56 percent of average. This was the 13th driest August on record since 1895, based on preliminary data.
The driest area was south of and parallel to Interstate 74 (Figure 1). Rainfall amounts in that region were generally an inch or less. One of the driest spots in Illinois was Lovington (Moultrie County in east-central Illinois) with only 0.03 inches for the entire month. Other familiar sites with extremely low readings included: Decatur with 0.15 inches, Springfield with 0.25 inches, and Quincy with 0.25 inches.
Only northern Illinois received average to above-average rainfall in August (Figure 2). One of the wettest spots in Illinois was Morris (Grundy County) with 7.02 inches, followed closely by Earlville (LaSalle County) with 7.01 inches.
Moderate to severe agricultural drought arrived in Illinois in August (Figure 3), according to the US Drought Monitor. This was the result of much less than average rainfall in July and August, as well as warmer than average temperatures. Damage to corn and soybean crops appears to be significant in places. However, the full extent of the damage will not be known until harvest.
Temperatures were above average for much of Illinois (Figure 4). Highs in the 90s and even low 100s were common across the state. The hottest spots in the state were Cairo with 103 degrees on August 4 and Bentley with 103 degrees on August 25. Both Quincy and Grand Chain Dam were close with 102 degrees on August 2 and August 4 respectively.
The statewide mean temperature (an average of both the high and low temperatures) was 74.9 degrees, 1.2 degrees above average.
Extreme Dryness in August for Much of Illinois
While the rains continue in northeastern Illinois, much of the rest of the state has been bone dry in August. Rainfall totals range from 3-5 inches in the Chicago area to less than an inch in many locations across central and southern Illinois. This band of dryness extends from southern Minnesota, eastern Iowa, Illinois, and into parts of Indiana and Kentucky (see first map).
Rainfall departures are on the order of 1-2 inches below average in the driest areas. Some of those same areas received little rainfall in July. The US Drought Monitor has much of central and southern Illinois in at least “moderately dry” with “moderate drought” in the central region of the state.
Of particular concern to me is that the few opportunities for substantial rain in August across central Illinois have resulted in only scattered showers/thunderstorms at best. There is another chance of rain on Tuesday/Wednesday but the projected amounts are on the order of 0.25 inches or less.
Update: USDA, National Ag Statistics Service (NASS) released the following on Illinois topsoil moisture (percent) by crop reporting district:
| District | Very Short | Short |
|---|---|---|
| Northwest | 4 | 21 |
| Northeast | – | 18 |
| West | 49 | 44 |
| Central | 31 | 38 |
| East | 40 | 44 |
| West Southwest | 26 | 58 |
| East Southeast | 13 | 46 |
| Southwest | 20 | 40 |
| Southeast | 30 | 56 |
| State | 25 | 41 |
Summer – One of the Warmest and Wettest on Record
Summer
This summer was one of the warmest and wettest in Illinois history, based on preliminary data. The average statewide temperature for this summer (June-August) was 76.4 degrees, 2.7 degrees above normal and the seventh warmest summer on record. The average statewide rainfall was 16.7 inches, 5.2 inches above normal and the sixth wettest summer on record. Statewide records for Illinois extend back to 1895.
August
The average statewide temperature for August was 76.8 degrees, 3.2 degrees above normal. That puts it at the 13th warmest August on record. August was on track to being even warmer but a late-month cool spell knocked it down a few notches in the ranking. August rainfall has been close to normal with a statewide average of 3.4 inches, just 0.3 inches below normal.
[This is an update of a post earlier in August, now removed to avoid confusion]