CHAMPAIGN — The preliminary statewide average January temperature was 31.4 degrees, 5 degrees above the 30-year normal and the 17th warmest on record going back to 1895, according to Illinois State Climatologist Trent Ford at the University of Illinois’ Illinois State Water Survey.
The preliminary statewide average total January precipitation was 4.41 inches, 2.34 inches above the 30-year normal and the ninth wettest on record.
Following a warmer than average December, temperatures remained persistently above average for the first half of January. Average temperatures in January ranged from the mid-20s in northern Illinois to the high 30s in southern Illinois and were 2 to 7 degrees above average across the state.
The highest temperature recorded across the state in January was 65 degrees in Cairo and Carbondale on Jan. 11.
Temperatures since the start of meteorological winter on Dec. 1 were 2 to 7 degrees above the long-term average across the state. Through Feb. 2, this winter has been the fourth warmest on record in Moline with an average temperature of 31.1 degrees. Interestingly, the three winters that were warmer through Feb. 2 in Moline are 2002, 2012, and 2016.
Warmer conditions have helped make for a mild winter so far across the southern half of the Midwest, as indicated by the Accumulated Winter Season Severity Index (AWSSI). AWSSI uses a daily accumulation of points, based largely on temperature, to characterize winter season severity.
Despite an early snowfall last fall, all AWSSI-monitoring stations in Illinois have indicated a mild or moderate winter season so far.
January total precipitation was above normal across the state, with monthly precipitation totals ranging from 2 inches in northwestern Illinois to nearly 8 inches in south-central Illinois.
The highest accumulation was along the Interstate 70 corridor between the St. Louis Metro East and Effingham. This region experienced nearly 300 percent of its average January total precipitation.
Vandalia in Fayette County experienced its third wettest January on record with 7.99 inches, over 5 inches above the long-term average. As with most of the wettest parts of the state last month, Vandalia received over 80 percent of its total monthly precipitation in just three days. Much of this was the result of a single winter storm that moved through the Midwest between Jan. 9 and 12.
Three-day precipitation totals between Jan. 10 and 12 broke three-day total January precipitation records at Charleston (5.85 inches), Taylorville (4.35 inches), Champaign (3.63 inches), and Marseilles (3.41 inches).
This event resulted in flooding along many of Illinois’ larger rivers, including the Kaskaskia River breaking through the Vandalia levee and causing a temporary closure of highway 51. Rivers crested between 24 and 72 hours after the precipitation ended. As of the end of the month, minor flooding persisted in only the lower Illinois and Kaskaskia Rivers in the state
Snowfall totals this last month ranged from less than a tenth of an inch in southern Illinois to over 12 inches in northwestern Illinois. The highest January snowfall total was 15 inches in both Stephenson and Bureau Counties. Rockford experienced the highest one-day snowfall maximum with 6 inches on Jan. 25.
January continued the longer winter season snowfall patterns, with the western third of the state experiencing slightly above normal snowfall since Oct. 1, and the eastern two-thirds of the state experiencing near normal to well below normal snowfall over the same period.
A broad area along the Indiana border from Cook County to Lawrence County has experienced between 50 and 75 percent of normal winter season snowfall, whereas most of the state south of Interstate 64 has experienced less than 50 percent of normal snowfall since Oct. 1.
In contrast, snowfall totals across a broad area between Jo Daviess County and Madison County in western Illinois has experienced between 100 and 125 percent of normal snowfall.
Short-term 8–14-day outlooks from the NOAA Climate Prediction Center show strongly elevated odds of above normal precipitation, with the highest probabilities across the southern two-thirds of the state. Short-term temperature outlooks show slightly elevated odds for a continuation of above normal temperatures across the eastern part of the state.
Longer-term 30-day outlooks show elevated odds of both above normal temperature and above normal precipitation in southern Illinois. Seasonal outlooks for spring (March to May) continue to show elevated odds of above normal precipitation across the state, with an equal chance of above normal, normal, and below normal temperatures.
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