Fall Climate Summary

 Fall Summary

Meteorological fall (September through November) saw a return of near to above normal rainfall, after a very dry spring and fall.  Rain totals for the three month period were 100-130% of normal for most of central and southeast Illinois (left image, click to enlarge).  Much of the surplus was due to an extremely wet September which saw 6-12" totals for much of the area.  The remnants of hurricane Isaac during the first couple days of  September produced much of this excess.  This allowed the severe/extreme drought conditions in early fall to ease to moderate drought/abnormally dry by late fall.  Fall temperatures averaged a few degrees below nomal across the region (right image). 

% of normal rainfall (Sept-Nov).  Image courtesy of the High Plains Regional Climate Center.

September through November departure from normal temperature.   Image courtesy of the High Plains Regional Climate Center.

September through November % of normal precip

September through November departure from normal temperature

Links below are the seasonal climate summaries for area cities. Only the summaries for Peoria, Springfield and Lincoln are considered "official", meaning they are the station of record for their respective locations. The other summaries are "supplemental", meaning another location in the area is the official climate station for that city.


Climate data for other area cities is available at http://www.nws.noaa.gov/climate/xmacis.php?wfo=ilx

September Highlights

After the extremely low rainfall that occurred during the spring and summer months, September was unusually wet for eastern and southeast Illinois. Amounts of 6 inches or more occurred over much of east central Illinois, while areas in far southeast Illinois received in excess of a foot of rain during September! Some of the highest totals were reported in Clay County, where specific amounts include 14.37" near Clay City, and 14.20" at Flora. In Olney (Richland County), 9.64" fell this month. However, such high amounts did not occur over the entire area. Farther northwest, the western portions of central Illinois only received near normal to slightly below normal rain. In fact, the Springfield's Capital Airport ended up 0.01" below normal for the month with only 2.89".

The above normal rainfall for much of the region was caused by two factors: (1) The remnants of Hurricane Isaac which impacted the area Aug. 31 through Sept. 3, and (2) a return to an active storm track which brought several rounds of moderate to heavy rains to the southeast third of Illinois. As a result, drought conditions eased. Before the rains of Isaac most of the area was in severe to extreme drought. But by the end of the month the extreme drought conditions had disappeared and severe drought was confined to several counties northwest of Lincoln, including the Peoria and Galesburg areas. Farther southeast where most of the beneficial rains fell (2 to 3 times normal), the drought had eased to moderate or even just abnormally dry by late month

Severe weather was limited during the month. Several weak tornadoes developed on Saturday, September 1, when the remnants of Hurricane Isaac moved north into the area. These tornadoes touched down north of Peoria, in rural portions of Stark, Marshall, and Woodford counties. Other severe weather events occurred on September 5, 7, and 21, when scattered thunderstorms produced hail and isolated damaging winds.

Temperatures across the region averaged 1 to 3 degrees below normal for the month. This was the second month in a row of below normal temperatures, after January through July all recorded above normal temperatures. Only one daily record was set: Springfield tied a record low of 33 degrees on September 24. Lincoln recorded their 9th coldest September on record.

October Highlights

Continuing the trend of wetter than normal weather that began in September, much of central and southeast Illinois saw rainfall amounts between 3 and 6 inches during October (center image, click to enlarge). The heaviest amounts were in a corridor extending from around Beardstown and Meredosia, east through Lincoln, to around Danville and Hoopeston. In these areas, rainfall totals of 5 to 6 inches were common, including widespread 2 to 3 inch amounts that fell on the
13-14th. By the end of the month, the lingering drought conditions were mainly confined to the Illinois River Valley northwestward (lower right image).

Average temperature departure from normal for October.  Information courtesy of High Plains Regional Climate Center.

October 12 rainfall.  Image courtesy of the High Plains Regional Climate Center.

Drought monitor as of October 30

October 2012 temperatures versus normal

October 2012 total rainfall

Drought status as of October 30

Temperatures averaged below normal (left image), ranging from 2 to 4 degrees below normal east of a Peoria to Olney line. Some of the more extended cool periods were from the 5th through the 12th, and again from the 26th through the 31st. A pair of sharp cold fronts brought significant temperature falls during the month. After high temperatures on the 4th that were in the lower 80s in most areas, highs were only in the middle to upper 40s the next two days, setting several records for coldest high temperature observed on those two days. A period of well above normal temperatures on the 21-25th came crashing to an end during the afternoon and evening of the 25th. As a cold front passed, temperatures in the 75 to 80 degree range plunged from 15 to 25 degrees in just an hour, and were in the 40s within a few hours. By the next morning, temperatures were in the upper 20s northwest of the Illinois River.

The remnants of Hurricane Sandy, which transitioned into a powerful extratropical storm toward the end of the month, impacted areas as far west as Illinois. Wind gusts on the 30th ranged from 25 to 40 mph, highest near the Indiana border, while further north, waves on southern Lake Michigan peaked in excess of 20 feet. Visit this link at the Chicago NWS web page for more information in that area.

November Highlights

In contrast to the previous two months, rainfall reverted to the trends of spring and summer, with much below normal totals in November. In fact, the entire region saw less than 50% of the typical monthly amounts (top center image, click to enlarge). Only one significant widespread rain event affected the area. On November 11-12 a general half to one inch of rain fell ahead of a cold front with the heaviest amounts occuring south of a Jacksonville to Springfield to Robinson line (top left image). By the end of the month, lingering drought conditions continued to affect areas northwest of the Illinois River, while the drought had largely eased for much of central and eastern Illinois (top right image).

November 11-12 rainfall.  Courtesy of SWOP network.

% of normal rainfall for November.  Image courtesy of the High Plains Regional Climate Center.

Drought monitor as of November 27

November 11-12 rainfall

November % of normal rainfall

Drought status as of November 27

November temperatures versus normal.  Image courtesy of the High Plains Regional Climate Center.

Thanksgiving High Temperatures.  Courtesy of COOP network.

November temperatures versus normal

Thanksgiving high temperatures

Temperatures averaged 1 to 3 degrees below normal (bottom left image), with the most significant departures over the eastern portions of the state. Several rounds of Canadian airmasses set up over the region through the month, and produced below temperatures on two-thirds of days. A couple noteable exceptions to the cold occurred. Ahead of the cold front which produced the Nov. 11-12 rains, sustained southerly flow brought record warmth to the area. Lows in the 50s and highs in the 70s were reported for the 10th-11th. Another period of well above normal temperatures for Thanksgiving (Nov. 22) saw highs in the 60s which was only a couple degrees shy of being the warmest Thanksgiving on record (bottom right image).


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