October Is Warm and Dry

So far, October in Illinois has been both warmer and drier than normal. As of October 19, the statewide average temperature was 59.8 degrees, 1 degree warmer than normal. The statewide average rainfall was only 0.22 inches, 12 percent of normal. See table below.
If this were July, the dryness would be a major source of concern. However, the impacts are much less in fall. In fact, the warm, dry weather aided in the maturing and harvesting of corn and soybeans. At the moment, the impacts are mostly focused on:

  • winter wheat – farmers are waiting on rains for germination;
  • landscaping – trees and shrubs may need more water before winter arrives;
  • fall color – I’ve noticed that the fall colors on trees and shrubs this year are muted with lots of shades of brown and yellow.

The NWS forecast shows a weather system moving through Illinois over the weekend. The potential rainfall amounts from this system range from 0.25 inches along the Wabash River in south-eastern Illinois to 1.25 inches in north-central Illinois. Another system is expected to move into the region on Tuesday/Wednesday. So the current dry weather may be short-lived.

                        10/01/2010 to 10/19/2010
Climate          <------Temperature----->   <---------Precipitation--------->
Division         Actual   Normal      Dev   Actual   Normal     Dev   Percent
Northwest          55.2     53.4      1.9     0.09     1.82    -1.73        5
Northeast          55.8     53.7      2.0     0.27     1.82    -1.56       15
West               57.6     56.3      1.4     0.10     1.90    -1.80        5
Central            56.7     55.7      1.0     0.22     1.86    -1.64       12
East               56.0     55.4      0.6     0.38     1.86    -1.48       20
West-southwest     58.0     57.5      0.5     0.13     1.72    -1.60        7
East-southeast     58.4     57.8      0.6     0.28     1.92    -1.65       14
Southwest          58.9     58.9      0.0     0.23     1.85    -1.63       12
Southeast          59.8     59.2      0.6     0.35     1.84    -1.49       19
State              57.3     56.3      1.0     0.22     1.84    -1.62       12
Dev means Deviation From Normal, Percent means Percent of Normal

Dry Conditions Persist in Illinois

Parts of southern and eastern Illinois have struggled with dry conditions since July/August. Those conditions have expanded in recent weeks across more of Illinois.  The latest U.S. Drought Monitor has slightly more than half the state in at least the “abnormally dry” category and 11 percent in “moderate drought”. Most of the impacts so far have been in agriculture and horticulture and not water supplies.
There is a strong La Niña occurring in the Pacific. Based on past events, Illinois is typically warmer and drier than normal during fall (September-November). By winter (December-February), the wetter than normal conditions typically appear in Illinois.

Outlook for Fall – Warm and Dry

NOAA’s Climate Prediction Center issued new outlooks today for October and beyond. The latest outlook for October shows all of Illinois having increased chances of being both warmer and drier than normal.
BTW, this is the exact opposite of how last October turned out. The statewide precipitation total in October 2009 was 8.40 inches. That was 5.5 inches above normal and the 2nd wettest October on record. The statewide average temperature was 49.6 degrees. That was 4.6 degrees below normal and the 6th coldest on record.
The outlook for October-December shows all of Illinois having an increased chance of warmer than normal conditions. Precipitation has “equal chances” of being above, below, and near-normal, or what I call a neutral forecast.

NOAA CPC forecast for this fall. Click to enlarge.

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.