SPRINGFIELD, IL--Preliminary data for Illinois indicate that September’s 3.61 inches of rainfall was 0.43 inches above normal, but conditions varied widely. From just south of St. Louis to Champaign and over to the Quad Cities, rainfall has been below normal. Yet rainfall in far southern Illinois and around Chicago has been much above normal, including a one-day total of 4.16 inches in Morris (near Chicago) on September 13 and 9.80 inches at Smithland Lock and Dam along the Ohio River in southeastern Illinois, the largest monthly total reported in Illinois.
“Temperatures dropped 2.5°F below normal for the first time this year. This was the 15th coolest September on record with a statewide average temperature of 63.7oF. Even so, the first nine months of 2006 had temperatures 2.3°F above normal and rank as the 9th warmest January–September since records began in 1895. Extremes ranged from 92oF at Belleville on September 17 to 33oF at Streamwood on September 29,” said State Climatologist Jim Angel of the Illinois State Water Survey (http://www.sws.uiuc.edu), a division of the Illinois Department of Natural Resources.
The National Weather Service’s Climate Prediction Center (CPC) has been watching a developing El Niño. An El Niño causes weather changes around the world and refers to warmer-than-normal waters along the Equator in the eastern Pacific Ocean.
The biggest impacts for Illinois occur in winter but only during the strongest of events, such as the one in 1997–1998 when statewide temperatures were 6°F above normal and seasonal snowfall was 5.6 inches below normal. Current consensus is that this will be only a moderate El Niño so impacts on Illinois may be less. Nonetheless, the CPC winter forecast for Illinois calls for an increased chance of temperatures above normal across Illinois and precipitation below normal in the southern two-thirds of the state.