August Near-Normal But Summer Hot, Dry for Illinois

August

After months of exceptionally warm temperatures and drought, Illinois finally experienced temperatures and precipitation closer to normal in August.
The statewide average temperature for August was 73.5 degrees, just 0.1 degree below normal. That’s about as “normal” as you can get.
The statewide average precipitation for August was 3.4 inches, which is 95 percent of normal. In the map below, areas in yellow and orange had 3 to 5 inches, while the areas in red had more than 6 inches. Areas in northern and western Illinois in green received less than 2.5 inches. The largest rainfall total in the state was at Grayville in southeast Illinois with 10.69 inches. In second place was Hoopeston with 8.33 inches.

Summer

The statewide average temperature for the three summer months of June, July, and August was 76.1 degrees, 2.6 degrees above normal. It was the eighth warmest summer on record in Illinois. The warmest was 1936 at 78.6 degrees.
The statewide average precipitation for June-August was 6.64 inches, 5.21 inches below normal. It was the sixth driest summer on record in Illinois. The driest was 1988 with 6.17 inches.

Year to Date

The statewide average temperature for January-August was 59.0 degrees, 4.2 degrees above normal. It was the warmest January-August on record in Illinois. The second warmest was 1921 with 58.3 degrees.
The statewide average precipitation for January-August was 17.45 inches, 7.31 inches below normal. It was the fourth driest January-August on record in Illinois. The driest was 1936 with 14.95 inches, followed by 1988 with 17.12 inches, and 1934 with 17.41 inches.

August precipitation for the last 30 days through the morning of August 31. Source: NWS. Click to enlarge.

Latest Seasonal Outlook

NOAA’s Climate Prediction Center released their June and June-August outlook yesterday (figure below). On the left hand side of the figure, they have far southern Illinois with an increased chance of above normal temperatures for June. For June-August, that area of increased chances expands and covers an area roughly south of I-70.  The rest of the state has “EC” or equal chances of above, below, or near-normal temperatures. In other words, they don’t see anything to push temperatures one way or another.
It’s the same story with precipitation – equal chances of above, below, or near-normal precipitation across the state for June and June-August. I think its fair to say that our current skill is pretty low in forecasting summer-time precipitation months in advance.

NOAA’s Climate Prediction Center outlook for this summer. Click to enlarge.

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]

Dry Weather in Southern and East-Central Illinois

After a wet start to the 2010 growing season, two areas of dryness have persisted in the last 60 days (see map below). The first area is far southern Illinois, where dry conditions extend back to June. The second, more recent area is in east-central Illinois. The hardest hit area appears to include parts of the following counties: McLean, Ford, Livingston, Iroquois, and Kankakee. Rainfall in that area has been between 25 and 75 percent of normal. Meanwhile, temperatures during that same period have run about 2.5 degrees above normal.
As expected, topsoil moisture in east-central Illinois has declined rapidly in recent weeks. According to the latest USDA NASS report, the “East” Crop Reporting District (CRD) in the heart of the dry area is showing that 35% of the fields sampled had “very short” and 48% of the fields had “short” topsoil moisture.
In southern Illinois, the percentages of fields with “very short” to “short” topsoil moisture are as follows:

  • East Southeast CRD: 16 % “very short” and 43% “short”
  • Southwest CRD: 17% “very short” and 65% “short”
  • Southeast CRD: 66% “very short” and 12% “short”
60-day rainfall departure
The 60-day (July 2 - August 30) rainfall departure from normal for the Midwest.