The U.S. Drought Monitor just increased the drought coverage in Illinois to 100 percent. In addition, the area of D2 “severe drought” expanded in eastern Illinois and east of St. Louis and along the Illinois-Wisconsin border.
The statistics for July so far (July 1 – 11) show why the drought has worsened so quickly. The statewide average precipitation was 0.5 inches, just 37 percent of what we would normally receive in the first 11 days of July. The statewide average temperature during this time was 83.1 degrees, 7.5 degrees above normal.
The table that accompanies the map has some interesting statistics. A year ago at this time there was no drought in Illinois thanks to an exceptionally wet spring and early summer. And this year started out with no drought in Illinois. Even three months ago only a small part of southern Illinois (5 percent) was considered in a moderate drought.
The U.S. Drought Monitor is a joint effort between NOAA, USDA, and the National Drought Mitigation Center. They do consider local input on drought impacts. If you have any impacts – text and/or picture – that you would like to include for consideration, please contact me at jimangel@illinois.edu – thank you.
Latest Soil Moisture and Drought Monitor for Illinois
Observed Soil Moisture
The Illinois State Water Survey has been monitoring the soil moisture at 19 sites around the state. The soil moisture is measured with probes set at specific depths at each site. It is reported as the fraction of water in the soil by volume. Most of the non-sandy soils in Illinois can hold up to 30-40 percent water by volume in the spaces between the soil particles.
Current observations in the driest areas of the state show significant declines at 2, 4, and 8 inches since early March. At the Peoria site, in the heart of the dry area, the fraction of water in the soil is only 15 percent at 2 inches, 18 percent at 4 inches, and 22 percent at 8 inches. The 20-inch depth has remained unchanged at 32 percent. By comparison at the end of April of last year, the fraction of water in the soil at those depths were all in the 35-40 percent range.
We are in the process of getting these data online in the next few weeks. Stay tuned.
U.S. Drought Monitor
The latest U.S. Drought Monitor map for Illinois shows an expanded area of D0 “abnormally dry” weather across the central part of the state between Interstates 70 and 80. A small area of D1 “moderate drought” is located in the area centered on Logan County. Another small area of D0 is in southeastern Illinois.
Dry Weather Across the Eastern Corn Belt
If you look at the Corn Belt this spring you see two different stories. Much of the western Corn Belt has enjoyed above normal rainfall if you look at the last 30 and 90 days (first two maps below). However, below normal rainfall was common across much of Illinois, and parts of Indiana, Ohio, Kentucky and southeastern MO. Those areas have widespread rainfall departures of 2 to 4 inches in the last 90 days. A few isolated spots scattered across Illinois have departures of 4 to 6 inches. A particularly dry spot in southeastern Illinois, southwestern Indiana, and western Kentucky has rainfall departures of 6 to 8 inches at 90 days.
This has definitely had an effect on streamflows (third map) and soil moisture (fourth map). Keep in mind that while the streamflows are low for this time of year, it is relative to the normally high streamflow in spring. The same would be true of soil moisture.
The last map shows the U.S. Drought Monitor depiction for Illinois as of April 17 with a large swath of “abnormally dry” conditions across central and southeastern Illinois.
There are some opportunities for rainfall between now and Saturday but the expected amounts are modest at 0.5 to 1.0 inches total. In the past few weeks, the forecasts have been overly optimistic about rainfall amounts. This is likely the result of the soils drying out, cutting off the local source of atmospheric moisture (humidity).
Dry October in Illinois
Precipitation
The statewide average precipitation for October in Illinois was 1.79 inches, 1.12 inches below average or 61 percent of average. That makes it the 21st driest October on record back to 1895. See map below.
Amounts of less than an inch were common in western Illinois. The driest spot for October in Illinois was Colchester (near Macomb) with 0.22 inches for the month. The wettest spot in Illinois was Lansing (south Chicago) with 5.22 inches.
Moderate to severe drought remains in western Illinois, according to the U.S. Drought Monitor. The National Weather Service has predicted above-average precipitation for November across Illinois. Combined with cooler temperatures, this should lead to improvements in that area of the state.
Temperature
The statewide average temperature for October in Illinois was 55.1 degrees, just 0.5 degrees above average. The highest temperature for October in Illinois was 92 degrees at Bentley on October 8. The lowest temperature was 23 degrees at Mt. Carroll on October 29. Most of Illinois experienced temperatures at or below freezing by the end of the month.
Snowfall
No measurable snow reported yet. I’m sure that will change in November.
