Summary: So far in December temperatures have been 5.6 degrees above normal, while the statewide average precipitation has been 0.28 inches, a tenth of normal. The NWS released their outlook for the rest of this winter. Colder than normal conditions are favored in Illinois in January. Colder and wetter conditions favored in January through March. Wetter conditions favored for most of Illinois in April through June.
December (as of 12/21/2017)
So far things have been quiet for December in Illinois. The statewide average temperature is 35.5 degrees and 5.6 degrees above normal. Based on the forecasts, we can expect much colder conditions for the rest of December and we will be much closer to the statewide 1981-2010 normal of 29.9 degrees by the end of the month.
The statewide average precipitation is only 0.28 inches (left panel below). That is only about one-tenth of the normal 2.74 inches we receive in December. The driest December on record for Illinois was in 1976 with only 0.44 inches. We could come close to beating that record at the rate we are going.
Snowfall has been light in northern Illinois and mostly a no-show in central and southern Illinois (right panel). By the way, precipitation is a measure of both the rainfall and the water content in the snow.
January through March
For January (top row), climate conditions are favorable for colder than normal temperatures across Illinois and the Great Lakes. Meanwhile, there are no indications that January will be either wetter or drier than normal in Illinois. The Ohio River Valley is favored to have wetter than normal conditions in January that includes the far southeastern portion of Illinois.
For January through March, colder than normal conditions are favored in the northern two-thirds of Illinois. The odds are strongest in northeast Illinois (sorry Chicagoland). There are no indications that the southern third of Illinois will be either warmer or colder than normal. Wetter than normal conditions are favored across Illinois as well as the Great Lakes and Ohio River Valley.
The NWS doesn’t do seasonal snowfall forecasts. However, colder and wetter conditions in winter are highly correlated with more snowfall – just saying. My fearless forecast is that we will see more snow than last winter when the state-wide average was only 9.6 inches and the second lowest on record.
April through June
The outlook for April through June (below) shows that warmer than normal conditions are favored in the southern half of Illinois as well as much of the southern two-thirds of the US. Climate conditions do not favor warmer or colder than normal temperatures in northern Illinois.
Most of Illinois is favored to have wetter than normal conditions and is part of the wetter pattern across the Great Lakes region.