September was Dry and Warm in Illinois
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[October 11, 2017]
The statewide average rainfall in September
was 0.78 inches, 2.45 inches below normal and the 5th driest
September on record, according to Illinois State Climatologist Jim
Angel at the Illinois State Water Survey.
The driest September on record since 1895 was in 1979 with 0.46
inches of rain.
Nearly all of the state had below normal rainfall in September.
Total monthly rainfall ranged from 4.16 inches in Rock Island to
only 0.01 inches at the Springfield airport. The only wet areas
were around the Quad Cities and a few spots along the Ohio
River, which benefitted from the remnants of Hurricane Harvey.
The August–September period was the 4th driest for those two
months in Illinois with a statewide average rainfall of 3.11
inches, which is 3.70 inches below normal.
With dry conditions in the past two months, the U.S. Drought
Monitor classified nearly 80 percent of Illinois as “abnormally
dry” and 13 percent as in “moderate drought.”
The statewide average temperature for Illinois was 68.7 degrees,
2.5 degrees above normal and the 28th warmest September on
record. Although the month started out on the cool side, a
late-season heat wave struck in the second half of September
with a number of sites routinely reporting highs in the mid- to
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Some of the warmest readings in the state were in Effingham and
Neoga, which both reported a high of 98 degrees on September 23. On
that date, the Chicago O’Hare Airport reported a temperature of 95
Statewide, many weather stations tied or broke daily high
temperature records with the September heat wave. In all, 202
records were broken and another 71 were tied in Illinois, based on
the potential number of stations with long-term records.
The National Weather Service forecasted an increased chance of a
warmer than normal October for all of Illinois and the eastern half
of the U.S., as well as the Southwest. In terms of precipitation,
northern Illinois is near the region with an increased chance of
wetter weather that extends across the upper Midwest and the High
Plains. Meanwhile, southern Illinois is in an area with an increased
chance of drier weather that is roughly aligned with the Ohio River
The Illinois State Water Survey at the
University of Illinois at Urbana-Champaign, a division of the
Prairie Research Institute, is the primary agency in Illinois
concerned with water and atmospheric resources.