Warm year in Illinois ends with a cold, dry December

[January 05, 2018]    The sixth warmest year on record in Illinois was 2017 with a statewide average temperature of 54.3 degrees, or 2 degrees above normal, in spite of the extreme cold ending to December.

Eight out of the 12 months in 2017 brought above-normal temperatures, according to Illinois State Climatologist Jim Angel of the Illinois State Water Survey at the University of Illinois. Illinois experienced the warmest February on record with a statewide average of 41 degrees, 10.1 degrees above normal.

On the other hand, Illinois’ 10th coolest August on record came in 2017 with a temperature of 70.5 degrees, 3.1 degrees below normal.

The statewide average precipitation for the year was 37.65 inches, 2.31 inches below normal, despite the dramatic precipitation events that occurred in 2017, such as the heavy rains in southern Illinois in spring, and in northern Illinois in July and September. Illinois received 6.86 inches of rain in April, 3.08 inches above normal, and the fifth wettest April on record. Still, Illinois experienced its fifth driest September on record with only 0.82 inches, 2.41 inches below normal.

Some exceptionally dry areas still exist in central Illinois, around St. Louis, and parts of southeastern Illinois. These will be areas to watch in spring for the 2018 growing season.

Snowfall for the 2017-2018 winter season started slowly, but with some significant accumulations by the end of December. Snowfall totals ranged from 6 to 15 inches in the northern half of the state and down to almost zero in far southern Illinois by December 31.

Cissna Park (Iroquois County) reported the largest winter snowfall total of 15.5 inches. Mt. Carroll (Carroll County) was in second place with 10.8 inches, and Chatsworth (Livingston County) was in third place with 10.5 inches.

The statewide average precipitation total for December in Illinois was 0.86 inches, 1.83 inches below normal and the eighth driest December on record. Far southern Illinois received 1 to 3 inches of precipitation, but the rest of the state received less than an inch.

December temperatures in Illinois were exceptionally mild until Christmas Eve. The cold and warm weather balanced out in December, leaving the statewide average temperature for the month at 28.9 degrees, 1 degree below normal.

The largest snowfall totals stretched from the Quad Cities and passed just south of Chicagoland. Overall, the state remained below normal on December snowfall.

[Lisa A. Sheppard]