A warm start to January, followed by an abundance of snow and record breaking cold!

January 2019 will be a month remembered by an unseasonably warm start, followed by several cold air outbreaks and a torrent of winter storms that finally made it feel like January in the Midwest. The last two days of the month brought a monumental Arctic air outbreak that shattered many record cold temperatures across the state.

January ended cooler, and substantially wetter than the long term average.  The preliminary average statewide January temperature was 24.7°F, which is -1.7°F below the long term average.  The preliminary average statewide precipitation was 3.51 inches, which is 1.44 inches above the long term average.

Data are provisional and may change slightly over time


State Record Cold Temperature in Jeopardy:

A National Oceanic and Atmospheric Administration (NOAA) cooperative (COOP) weather observer at Mt. Carroll (Carroll County) reported a temperature of -38°F  on the morning of January 31st.  This unofficial temperature is currently under review by the State Extremes Committee, and if confirmed with be a new state record.  The current record is -36°F recorded in Congerville (Woodford County) on January 5, 1999.

In addition, multiple all time station record lows were set in Illinois on the morning of January 31st.  Some notable records include, Moline (Rock Island County) with a reading of -33°F , and Rockford (Winnebago County) with a reading of -31°F, as reported by the National Weather Service.

Preliminary results show that January 2019 finished with a statewide average temperature of 24.7°F which is -1.7°F degrees below the long term average.

January temperatures were a roller coaster over the course of the month, as depicted in the plot below, showing high and low temperatures and averages for Champaign-Urbana throughout the month.  Champaign-Urbana was chosen since the State Climate Office is located here, but this trend can be representative of the state as a whole.

Trends in temperatures across the entire state are depicted in the maps below.. The first 10 days of January saw statewide average temperature departures of around +9 to +14 degrees.  On the reverse end, looking at the last 10 days of the month, we experienced average temperature departures of around -5 to -21 degrees in a south to north pattern across the state.  The most extreme departures were in Northwest Illinois.

Temperatures for the month as a whole were closer to the long term average (see map below).  Regions near, and south of I-70 generally reported departures of one to three degrees above the long term average.  However, many locations in Northern Illinois reported departures of one to three degrees below the long term average, while the central portion of the state was near to slightly below average.

  • The highest temperature recorded for the month, was 66°F which occurred at two separate stations, Grand Chain Dam (Pulaski County) on January 2nd, 2019, and Jerseyville (Jersey County) on January 8th, 2019.
  • The lowest temperature recorded for the month was -38°F* at Mount Carroll (Carroll County) on January 31st, 2019 – *this recording is currently under review by the State Extremes Committee.


Preliminary statewide average precipitation for January was 3.51 inches, which is 1.44 inches above the long term average.

An active weather pattern beginning in the middle of the month allowed several large weather systems, and numerous smaller clipper type systems to traverse the state.  These storms were accompanied by heavy rains, accumulating snowfall, and sometimes icy precipitation.  The heaviest precipitation fell in the south/southwestern portion of the state where 5 to 6+ inches were measured (see first map below).  Many regions in Central and Northern Illinois received well over 100% of their average January precipitation, with Northwest Illinois receiving 200 to 300% (see second map below).

  • The highest monthly rainfall total of 6.50 inches occurred at a station near Cobden (Union County), 1.50 inches of which fell in a single day on January 5th, 2019.


Snow was abundant across the state in January, with all of Illinois recording at least some accumulating snowfall.  The highest snowfall totals of 15 to over 20+ inches were common in West-central and Northwest Illinois (see map below).

These same regions generally recorded accumulations on the order of 10 to 15+ inches above the long term average.

  • The highest monthly snowfall total was from Moline (Rock Island County) where 30.2 inches were reported, which is 20.8 inches above the long term average, ranking this as the snowiest January on record for the station.
  • Rockford (Winnebago County) received 24.9 inches, which is 14.7 inches above the long term average for January.
  • Chicago O’Hare reported a trace or more of snowfall for 15 consecutive days, from January 17th through January 31st.

Ice cover on Lake Michigan increased to nearly 35% by the end of the month, according to data from the Great Lakes Environmental Research Laboratory (chart below).

MODIS Imagery of Lake Michigan Ice Cover (Feb 1 2019)

Outlook for February 2019

Looking ahead at the rest of February 2019, the Climate Prediction Center is forecasting an above normal chance for a wetter than average February statewide. The highest probabilities are located toward the eastern side of Illinois.  Below average temperatures are favored for much of Central and Northern Illinois, with no strong signal further south.


2018 Illinois Climate Recap

 A Climatologic Review: 2018

Now that 2019 is well underway, lets take a moment to reflect back on the climate averages and departures from 2018.

Note:  Data are provisional and may change slightly over time


2018 was a year marked with several climatologically dramatic temperature swings.  The chart below shows monthly temperature departures from the 1980 – 2010 long term average for Illinois.  The most noteworthy feature is the -7.8°F departure that occurred in April, ranking April 2018 as the second coldest April on record for the state (records extend back to 1895).  And with the turn of a calendar page, May saw a +8.0°F departure from the long term mean, ranking May 2018 as the warmest May in state history.

The plot below shows the average statewide temperature (F) by month for 2018, the colors represent meteorological seasons.

The map below shows spatially average temperature departures for the year 2018.   Despite several dramatic temperature swings throughout the seasons, the year as whole finished right around the long term mean statewide.  A few regions in the northwest were a degree below, and a few regions in the south/southeast were a degree above the long term mean.

The statewide average temperature for 2018 was 52.5°F which is 0.2°F  above the long term average.

  • The highest temperature recorded in the state: MORRIS 1 NW in Grundy County with 100°F on May 28th, 2018
  • The lowest temperature recorded in the state:  MORRISON in Whiteside County with -24°F on January 1st, 2018
  • The warmest mean temperature: LAWRENCEVILLE 2WSW in Lawrence County with 59.3°F
  • The coldest mean temperature: PALESTINE in Crawford County with 43.1°F


The chart below shows monthly precipitation departures from the 1980 – 2010 long term average for Illinois in inches.  February saw the wettest departure from average at 2.82 inches.  April saw the driest departure from average at -1.36 inches,

The plot below shows the average statewide precipitation (in) by month for 2018, the colors represent meteorological seasons.

The map below shows precipitation as a percent of normal for the year 2018 in inches.  It was a rather wet year statewide, the highest percentages above average were reported in numerous regions across the extreme northern and southern portions of Illinois, where 125 to 150 percent of normal precipitation was measured.

The statewide estimated average precipitation for 2018 stands at 45.75 inches which is an impressive 5.79  inches above the long term average.

  • The highest yearly precipitation in the state: NASHVILLE 1E in Washington County, with 66.79 inches
  • Largest one day maximum event: CISNE 2.5 in Wayne County with 8.54 inches on September 8th, 2018
  • Snowiest location in the state: BULL VALLEY 2.5 WNW with 55.4 inches, the one day maximum snowfall for the site was 13.1 inches on November 26, 2018

Severe Weather

Severe weather reports for Illinois in 2018 from the NOAA Storm Prediction Center. Note: It is possible to generate multiple report for the same storm/event

Month Total Reports Tornado Hail Wind
January 2 0 2 0
February 1 0 0 1
March 0 0 0 0
April 20 9 4 7
May 170 6 48 116
June 184 11 15 158
July 54 0 6 48
August 40 2 7 31
September 40 2 1 37
October 3 0 0 3
November 0 0 0 0
December 52 34 11 7
Total 566 64 94 408

Illinois Climate Minute: 2018 Recap

Thanks for reading!

Warm and Stormy December for Illinois

In contrast to November, December 2018 finished warmer than the long term average, was lacking in major winter storms, and brought a historic late season severe weather outbreak.

  • The statewide average temperature for December was 34°F, which is 4.1°F above the long term average.
  • The statewide average precipitation for December was 3.35 inches, which is 0.66 inches above the long term average.
  • The highest temperature recorded for the month was 71°F on December 2nd at the Kaskaskia River Lock and Dam in Randolph County.
  • The lowest temperature recorded for the month was 6°F on December 28th at both the Altona and Mount Carroll stations in Knox and Carroll Counties.
  • The highest monthly rainfall total of 6.83 inches occurred at a station near Chester, which is located in Randolph County.
  • The highest monthly snowfall total was only 3.1 inches, and was recorded at a station near Patoka in Marion County.
  • The National Weather Service confirmed 29 tornadoes in Illinois during the historic December 1st severe weather outbreak.

Data are provisional and may change slightly over time


December favored above average temperatures for the entire Midwest, including Illinois  The map below shows that the largest temperature departures were felt in the upper Midwest, and extending down into much of northern Illinois where several locations finished the month 6 to 7 degrees above the long term average.  Overall, the statewide average temperature for December was 34°F which is 4.1°F above average.


Statewide precipitation totals for December were at or above the long term average. Two storm systems impacting the state during the last week of December helped to bring the monthly totals above normal for much of central and northern Illinois, where precipitation was lacking in the middle of the month.  The highest widespread precipitation totals occurred around and south of I-70.  The maps below show total December precipitation, as well precipitation departures for Illinois.

December was not an ideal month for snow lovers as warmer temperatures, and a combination of environmental factors kept December snow accumulation to a minimum.  The highest accumulations were in the northeast, and in central/west central portions of the state –  where a quick moving cold front brought a majority of the snow accumulation during the first week of December. Total snow accumulations are shown in the map below.

Severe Weather

The National Weather Service confirmed 29 tornadoes across Illinois during the December 1st tornado outbreak, ranking this as the largest December outbreak in state history.  The previous three largest outbreaks are listed below:

  • December 18-19, 1957 with 21 tornadoes
  • December 23, 2015 with 6 tornadoes
  • December 4, 1973 with 5 tornadoes

Most notable was the Taylorsville Tornado in Christian County.  This tornado had a path width over 1/2 mile wide, and estimated wind speeds of 155 mph, ranking it as an EF-3 on the Enhanced Fujita Scale, The Taylorsville tornado caused major damage to 100 homes, and 22 reported injuries.

The map below, from the Storm Prediction Center, pinpoints locations of all severe weather reports from 12/1/2018.  It is evident that the worst of the severe weather, and tornadoes, were confined to west central Illinois.

SPC Storm Reports

In total, 52 severe weather reports were recorded for Illinois this December; 34 reports for tornadoes, 11 for severe hail, and 7 for severe wind.  Note:  It is possible for multiple reports to be created for the same event/storm.

Check out the Twitter link from Kevin Lightly, capturing aerial images of damage in Taylorsville the day after the tornado outbreak:

Outlook for January

Looking ahead at the rest of January 2019, the Climate Prediction Center is forecasting an above normal chance for a drier than average January for a majority of the state. The highest probabilities are centered over northern Illinois and the Great Lakes.  Focusing on temperatures, the highest probabilities for above average temperatures are concentrated over the upper Midwest and North Dakota, with a smaller probability extending into northwest Illinois.

January 2019: CPC One Month Precipitation Outlook
January 2019: CPC One Month Temperature Outlook

Be sure to check back in the coming week for the ‘Illinois 2018 Climate and Weather Recap’ blog entry.



Cold, Snowy November in Illinois

It was a cold and snowy November in Illinois.

  • The statewide average temperature for November was  35.2°F, which is an impressive 7.3°F below normal, ranking November 2018 as the 8th coldest on record.
  • The statewide average rainfall for November was 3.11 inches, which is 0.36 inches below normal.
  • The highest temperature recorded for the month was 70°F at a station in Du Quoin on the 1st day of the month.
  • The coldest temperature recorded for the month was a chilly 1°F at three stations in Lee, Carrol, and Knox County on the night of the 28th.
  • The highest monthly rainfall total of 7.50 inches occurred at a station in Belknap, which is located in Massac County.  5.51 inches of the total was recorded during a one-day event on the 1st of the month.
  • The highest monthly snowfall total of 18.5 inches was recorded at a station in Bull Valley, which is located in McHenry County.

November was an exceptional month for snow lovers statewide, with virtually the entire state seeing it’s first accumulating snow of the season before the month’s end.  In fact by the 15th, with half the month still to go, Springfield Abraham Lincoln Airport had already broken the record for the snowiest November.
Overall monthly snowfall accumulation totals averaged around an inch in southeastern Illinois, up to 15 inches in the northwest, near the Quad Cities, with several locally higher amounts reported.


Several outbreaks of unseasonably cold conditions throughout the month helped in bringing the statewide averaged November temperature to a chilly 35.2°F.
Temperatures across Illinois were typically on the order of 5 to 10 degrees below normal, a trend that was felt across most of the Midwest.  The map shows the bullseye for the below normal cold concentrated in sections of northeast Missouri, southeast Iowa, and west-central Illinois.

Seasonal Review

Looking at meteorological Fall (Sept, Oct, Nov), temperatures for the season ended up near normal in southeastern Illinois, and between 2 to 4°F below normal as you head northwest toward Rockford and the Quad Cities (see map).

Precipitation for the same period is near normal for the central portion of the state, with above normal totals in the northwest and southeast.  Precipitation totals at Chicago O’Hare and Rockford Airports are currently ranked as the 4th wettest years on record, with a month still to go.

December Outlook

Finally, here is the outlook for December that was released by the National Weather Service (NWS) Climate Prediction Center (CPC) on November 30th.  The precipitation maps show an increased chance of above normal precipitation statewide, becoming more likely as you head westward towards Nebraska.  Temperature wise, there is a slightly increased chance of above normal temperatures statewide, a trend which is noted for much of the eastern half of the country.

Notable November Events:

Rainy Start to November for Southern Illinois.

November started with several substantial rain events bringing a half to an inch and a half of precipitation to most of the state, with the largest amounts in southeastern Illinois.  Two CoCoRaHs stations in Massac County, and a COOP station in Pope County recorded over 6 inches of rain during the first week of November.

Mid-month Snowstorm and Canadian air outbreak.

An early season plowable snowstorm, accompanied by unseasonably cold temperatures affected much of the state November 14-15th.  As much as a half foot of snow was reported in locations south and west of Springfield.  The official total at Springfield Abraham Lincoln Airport was 5.3 inches. Total monthly snowfall accumulation in Springfield measured 11.4 inches, ranking November 2018 the snowiest November on record.

Northern Illinois November Blizzard.

A potent low-pressure system tracked through central Illinois to finish off the Thanksgiving weekend, bringing a wide range of weather to the state.  Thunder, rain, ice, snow, wind, and blizzard conditions were all reported in varying locations on Sunday 11/25/2018.  The map below shows station interpolated snowfall  totals for this event.
Peak wind gusts of 55 mph were reported at Champaign Willard Airport, and 52 mph at Chicago O’Hare.

The measured snowfall totals of 11.7 inches at Rockford, and 13.3 inches at Moline, ranks this event as the largest November snowstorm on record for both locations.  The total November accumulated snowfall in Rockford of 15.8 inches, and Moline of 18.4 inches ranks November 2018 as the snowiest November on record for both locations.
A fresh snow pack, coupled with cold air behind this system allowed temperatures to plummet during the start of the last week in November.  Both Moline, and Chicago O’Hare set a record low maximum temperature on 11/27/2018, with recordings of 22°F at Moline and 25°F at O’Hare.
This post was written by Brian Kerschner, who will be taking over the blog next month.

Heat, Frost, Snow, and Rain – Just a Typical October in Illinois

I love the weather in Illinois – hardly ever a dull moment.  This October we experienced days in the 90s, the first fall frost, the first snow of the season, and widespread heavy rains.
The statewide average temperature departure for the first 9 days of October was 11.5 degrees above normal.  There were many reports of temperatures in the 90s during this period, including a high of 94 degrees in Fairfield on October 7.
After the passage of a strong cold front, temperatures dropped and remained much cooler for the rest of the month.  The temperature departure from October 10-31 was 5.7 degrees below normal.   The warm and cold periods balanced out, leaving the statewide average temperature for October at 54.0 degrees, 0.4 degrees below normal.
Freezing temperatures arrived across most of Illinois on October 21st.  The lowest reported reading was 19 degrees at locations near Stockton, Shabbona, and Champaign.  Historically, the average dates for the first fall frost are in October across the state.
The first snow of the season fell on October 12th.  I happened to be driving through it between Kankakee and Champaign (photo below).  There were widespread reports of traces of snow, meaning it melted as it fell. A few areas reported a small amount of accumulation, including Moline and Bloomington with 0.2 inches.  We do not always see snowfall in October in Illinois, but it does show up in the records from time to time.  However, it is not a reliable indicator of the upcoming winter. IMG_2548
Precipitation was widespread across Illinois in October.  The statewide average was 3.81 inches, 0.57 inches above normal.  Amounts of 4 to 7 inches or more were common in the northern half of the state, which is well above normal. Meanwhile, most of the southern half of the state was drier with amounts in the 2 to 4-inch range, which is much closer to normal for October. The largest monthly total was 8.07 inches in Nauvoo (Hancock County).

Another interesting feature of 2018 so far in Illinois has been the impressive precipitation totals in northern Illinois.  Several stations have received over 50 inches of precipitation through October 31, including Elizabeth (Jo Daviess County) with 54.45 inches. That is 22.66 inches above normal! The maps below show the extent of the amounts over 50 inches scattered across the state (darker red), while a relatively drier band stretches from St. Louis to Chicago.


NOAA Outlook for Winter in Illinois

Today, NOAA released the official outlook for winter (December-February).  Not much to report for Illinois.  The northern third of the state has a slightly increased chance of a warmer than normal winter.  And northeastern Illinois has a slightly increased chance of a drier than normal winter. However, the increased odds are very weak and we are on the margins for those areas.  Historically, the core areas with higher odds on the NOAA maps (for example, the Northwest for temperatures) are more like to be proven correct.
Otherwise, the chances are even-Steven across Illinois for the three categories of above, below, and near-average winter temperatures and precipitation.  Maps below.
One of the most important factors for this winter will be the presence and strength of a possible El Niño event. Currently, there is a 70 to 75 percent chance that El Niño will arrive sometime this fall or winter.  El Niño occurs over the central and eastern Pacific Ocean and involves changes in the atmosphere and ocean circulation.  This, in turn, can affect our winter weather in the US.
Right now the official forecast indicates a weak El Niño, hence the anemic odds over Illinois.  If it had been stronger, the odds of a warmer-than-normal winter would be higher for us.  A weaker El Niño event could mean that other factors have a chance to play a bigger role in our winter weather. However, things like the Arctic Oscillation and the related Polar Vortex are much harder to predict more than a few days in advance.

Above-Normal Temperatures and Rainfall for September in Illinois

Based on preliminary data, Illinois experienced above-normal temperatures and rainfall for September in Illinois.  Here are the statistics for the state:

  • The statewide average temperatures for September was 70.0 degrees, 3.8 degrees above normal and the 12th warmest September on record.  We were on track to one of the warmest Septembers on record until the last cold snap.
  • The statewide average rainfall for September was 4.97″, 1.74″ above normal and the 19th wettest September on record.
  • The hottest temperature recorded for September was 99 degrees at Springfield Airport on September 5.
  • The coldest temperature recorded for September was 30 degrees at Ottawa on September 29.
  • The highest monthly rainfall total for September was 12.43″ at Clay City (just south of Effingham).

Here are the rainfall totals (left) and departures from normal (right) for September in Illinois (click to enlarge).  Rainfall was heaviest in southern Illinois with amounts up to 12 inches and in northwestern and western Illinois with amounts up to 10 inches – all well above normal.  There was a band of drier conditions stretching from St. Louis to Chicago where rainfall totals of 1 to 3 inches were common.

In addition, heavy rains fell across the upper Midwest in September (maps below, click to enlarge).  The rains were especially heavy in Wisconsin, Iowa, and Minnesota, leading to river flooding in Illinois along the Mississippi and rivers coming out of Wisconsin

Temperatures across the Midwest were much above normal in September (map below with pumpkin spice-colored shading – appropriate for this time of year).  While Illinois was 3.8 degrees above normal, Indiana was 4.5 degrees above normal, Kentucky was 5.0 degrees above normal, and Ohio was 5.5 degrees above normal.  The other states were 1 to 3 degrees above normal for the month.
Outlook for October
Finally, here is the outlook for October that was released by the NWS on September 30.  These rely heavily on the more reliable forecasts out to 14 days.  Those forecasts show Illinois with very strong chances for above-normal temperatures and rainfall. As a result, the October outlook also shows most of Illinois with an increased chance of above-normal temperatures and all of Illinois with an increased chance of above-normal temperatures.
On a side note, the 4-corners region (UT, CO, AZ, and NM) are in a severe drought and the expected rainfall will be welcomed there.  The same cannot be said for the Upper Midwest, which was already very wet in September.

See the page on normals for more on this topic.

Hot September So Far, But Relief Is in Sight

Illinois and the Midwest have been running hot so far in September.  The statewide average temperature for September 1-19, 2018, in Illinois was 73.5 degrees and 4.7 degrees above normal.
Days at or above 90 degrees have been quite common this September, especially in central and southern Illinois where we saw 8 to 12 days with temperatures at or above that threshold. Runs of hot weather like this in September are unusual but not necessarily record-breaking. For example, here in Champaign, we have reached the 90-degree threshold 10 times this month (including today).  That’s the 4th highest count for September since 1888.  The highest number of days was 15 set in 1897.
But this is about to change on Friday as a cold front sweeps across the state.  Here is the forecast map for Friday morning with rain ahead of the front and cooler temperatures behind the front.  The NWS forecasts out to 14 days show that colder-than-normal temperatures will prevail with highs in the 60s and 70s and lows in the 40s and 50s across much of Illinois.
From a harvest standpoint, the rains over the next five days may impact harvest with the heavier amounts expected in southern Illinois with potential amounts of 1 to 2 inches south of Interstate 70.  The expected amounts are much less in central and northern Illinois.  A look at the 6-10 and 8-14 day forecasts suggest that Illinois will continue to be in a wetter pattern with above-normal precipitation and below-normal temperatures.
The NWS also released their latest outlooks today.  For October there is a “blob” of cooler-than-normal conditions centered over Iowa and Missouri and includes western Illinois.  Illinois has “equal chances” or EC on precipitation, meaning there is not an increased chance of either above or below normal precipitation.
For October-December, Illinois has an increased chance of above-normal temperatures. There is not an increased chance of either above or below-normal precipitation.  For the most part, the temperature pattern for October-December is based on climate trends (warming) and the odds favoring the arrival of El Niño this fall and winter.

Both August and Summer Were Warmer, Wetter Than Normal for Illinois

August: the statewide average temperature for Illinois in August was 74.9 degrees, 1.3 degrees above normal.  The statewide average rainfall was 5.25  inches, 1.66 inches above normal and the 12th wettest August on record.
The warmest daily high temperature was 97 degrees reported at Chicago Botanical Gardens (8/5), Chicago O’Hare (8/4), Jerseyville (8/7), and Pittsfield (8/29).  The coolest reading was 42 degrees reported at Rochelle (8.22).
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