Tag: heat

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30-Day Dry Spot in Corn Belt

As of July 13, 2011, the map of 30-day precipitation departures (figure below) showed a large area of below-average precipitation extending from eastern Iowa, through Illinois and Wisconsin and into parts of Michigan, Indiana, and Ohio. At first, this was not a concern because of the wet conditions that occurred through much of the spring. However, the lack of rainfall and hot conditions in the first part of July have begun to dry out the topsoil in Illinois. The rainfall departures range from 0.5 to 3 inches below average across northern and eastern Illinois.
Comparing the NASS report for  July 5 and July 11:

  • the Northwest crop reporting district (CRP) went from 11% dry to very dry topsoil to 30% dry to very dry in one week
  • the Northeast CRP went from 4% dry to very dry to 29% dry to very dry in one week
  • the East CRP went from 12% dry to very dry to 37% dry to very dry in one week.

The potential loss of water from soils from evaporation and transpiration from crops is on the order of 0.2 inches per day in Illinois now (link to potential evapo-transpiration maps). That means that we need about 1.4 inches of rain per week in July just to keep up with the demand from the crops. If the crops don’t get the water from rainfall then they have to rely more on soil moisture. So a week with no rain and temperatures in the 90s can dry out the topsoil quickly.
According to the Crop Watchers in the Illinois Farm Bureau’s FarmWeek, corn and soybeans in the sandy soils and in the thin soils on the ridges are showing signs of stress. Today we have seen slightly cooler temperatures across Illinois, along with some rain. However, the NWS is forecasting a return of hot weather over the weekend. In addition the NWS 6-10 day and 8-14 day forecast show a greater chance of above-average temperatures across all of Illinois. Those forecasts show a greater chance of below-average rainfall across the southern two-thirds of the state and near-to-above average rainfall in the northern third of the state.
While northern Illinois has been dry, much of southern and western Illinois has received much-above average rainfall, by as much as 2 to 5 inches or more in many locations. The wet conditions have led to flooded fields and widespread planting/replanting delays.

30-day precipitation departure
The 30-day precipitation departure as of July 13, 2011. Area circled in red shows less-than-average amounts. Source NOAA. Click to enlarge.
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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.
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Record Streak of Warm Days in Chicago

From the National Weather Service

Record of Days At or Above 80 Degrees for Chicagoland

THE PREVIOUS RECORD FOR CONSECUTIVE 80 DEGREE OR ABOVE DAYS WAS 42
DAYS IN A ROW...SET IN 1955. ON AUGUST 13 2010...THE CHICAGOLAND
AREA HIT 43 CONSECUTIVE DAYS...AND THE NUMBER CONTINUES TO
INCREASE. JULY 2 2010 WAS THE FIRST 80 DEGREE DAY OF THE CURRENT
RECORD. AS OF 251 PM CDT TODAY...WHEN THE TEMPERATURE AT OHARE
INTERNATIONAL AIRPORT OFFICIALLY REACHED 80 DEGREES DURING
AFTERNOON HEATING...TODAY IS THE 46 CONSECUTIVE DAY FOR THIS
RECORD.
THE TOP TEN RECORDS ARE AS FOLLOWS
1.   46 DAYS...WITH THE STREAK STILL CONTINUING ON AUGUST 16 2010
2.   42 DAYS...WITH THE STREAK ENDING ON AUGUST 7 1955
3.   34 DAYS...WITH THE STREAK ENDING ON SEPTEMBER 6 1995
4.   32 DAYS...WITH THE STREAK ENDING ON AUGUST 8 1983
5.   30 DAYS...WITH THE STREAK ENDING ON JULY 19 1921
6.   29 DAYS...WITH THE STREAK ENDING ON AUGUST 18 1988
7.   27 DAYS...WITH THE STREAK ENDING ON AUGUST 6 1999
8.   27 DAYS...WITH THE STREAK ENDING ON JULY 14 1966
9.   25 DAYS...WITH THE STREAK ENDING ON AUGUST 15 2007
10. 24 DAYS...WITH THE STREAK ENDING ON JULY 26 2005
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First Half of August – Warm

The state-wide temperature in Illinois for the first half of August (August 1-15) was 79.5 degrees, 5.7 degrees above normal. That should come as no surprise to anyone who experience the hot, humid conditions in August.
The state-wide precipitation for the first half of August was 2.32 inches, just 0.41 inches above normal. The wettest conditions were in the northern third of Illinois with most locations reporting 2 to 5 inches of rain. Meanwhile parts of eastern and southeastern Illinois have been on the dry side, reporting less than 1.0 inches so far  in August. The rest of the state was close to normal (around 2 inches).

Illinois rainfall map
Rainfall map for Illinois for August 1-15, 2010