The deadly November tornadoes were the most significant weather event of a fall marked by generally normal temperatures and below-average rainfall, according to the National Weather Service.
The 10 tornadoes in the Chicago-area Nov. 17 were the most for November, the agency said. There were 25 tornadoes across the state, killing 7 people. Fourteen of those were EF-2 or stronger, including two EF-4 tornadoes, the second most-powerful storms possible.
One of those EF-4 storms struck Washington in Central Illinois with winds that reached 190 m.p.h.; it was the strongest in Illinois in November since 1950. That tornado's path was 46.2 miles across Tazewell, LaSalle and Livingston counties.
The agency said that the fall started with an abnormally warm September and early October that featured a 95-degree high temperature on Sept. 10 that tied a record. But cooler temperatures prevailed through late October and November. The result: An average high of 61.6 that was .2 degrees below the average from 1981 to 2010 and an average low of 43.6 degrees that was .4 degrees above normal.
The average mean temperature was 52.6 degrees, .1 degree above normal, the agency said. The highest temperature was the 95 on Sept. 10 and the lowest was 11 degrees on Nov. 24.
Precipitation for the fall totaled 7.78 inches, 1.73 inches below normal, though some areas hit hardest by fall storms may have totals that were 2 to 4 inches above normal. The biggest rainfall came across Oct. 30 and 31, when 1.59 inches fell in the Chicago-area, including 3.17 inches at Midway International Airport on the city's Southwest Side and 2.69 inches at the NWS office in southwest suburban Romeoville. It was only the 4th Halloween on record with more than an inch of rain.
There also was a total of .9 inches of snow, .5 inches below normal. A snowstorm on Oct. 22 dropped as much as an inch of snow in some areas of North-Central Illinois, according to the NWS. It was the second earliest snowfall on record since 1919 and only the sixth measurable October snowfall since 1919.