WFO Chicago

2007 Climate Summary for Chicago

                                Temperature                                                          Precipitation


Yearly Extremes:
Highest Temperature:
94 on July 8th and July 9th
Lowest Temperature:
 -10 on February 5th
Most Precipitation in One Day:
 2.35” on August 23rd
Most Snowfall in One Day:
8.8” on February 13th
Records set during 2007:
March 13th (73)
March 25th (79)
March 26th (79)
October 7th (87)
September 15th (39)
           Highest Min:
March 26th (63)
April 7th (32t)
October 7th (67)
            Lowest Max: 
14th Warmest March
11th Warmest October
32nd Warmest Year
            One Day Precipitation:
March 1st (1.09”)
March 21st (1.07”)
August 23rd (2.35”)
            Monthly Precipitation:
4th Wettest August
Seasonal Precipitation:
9th Wettest Summer
8th Driest Fall
           One Day Snowfall:
February 13th (8.8”)
April 11th (3.0”)
           Monthly Snowfall:
13th Snowiest December
           Seasonal Snowfall:
51st Wettest Year
The start to 2007 was a relatively mild one with the first two thirds of the month being above normal. However, most people thought that the month was below normal due to the last week of the month being cold and below normal for the first time all winter. January did end up being about 6 degrees above normal for the month. There were no records set during the entire month. 19 of the 31 days had a trace or higher of snowfall, but they were mainly flurries or just quick snow showers and not much accumulation with just 3.5 inches of accumulation for the whole month. The warmest temperature of the month was 52 degrees on the 4th and the coldest temperature was 3 on the 31st.
Winter returned with a bang during February, causing most people to forget about the mild December and January. Temperatures were well below normal for most of the month, with the average temperature ending up being 9 degrees below normal. There was quite a bit of snowfall as well, with 20.3” inches falling, which was double the amount that had fallen over the rest of the entire season up to this point. The biggest snowstorm of the month was on the 13th when blizzard-like conditions were felt throughout the region…especially further to the south toward central Illinois. A record amount of snow fell on this day at O’Hare, with 8.8” falling on the 13th. An ice storm occurred on the 24th, with a mixture of thundersnow, sleet, snow pellets, and freezing rain affected the region. The warmest temperature of the month occurred on the 21st when the high reached 48, while the coldest temperature was on the 5th when it dipped down to -10.
It has been a tale of three completely different months so far in 2007. January had quite a few days of snow, but was above average temperature-wise. February was very cold with a lot of snow. Then March came along and ended up being the 14th warmest March on record. Four high temperature records were broken, while two precipitation records were broken. The warmest temperature of the month occurred on the 25th and 26th when it reached 79, while the coldest temperature happened on the 8th when it dropped to 13. The month ended with a bang with a line of severe storms that developed in the evening of the 31st and moved through the Chicagoland area. Some apartment buildings were damaged from a microburst in Carol Stream with these storms.
Going into April, the region had been spoiled with mid to upper 70s at the end of March, so you just knew that something was going to come along to balance that out. A late season snowstorm came through the region with a sloppy, wet snow on the 11th and 12th. The 3 inches of snow that fell on the 11th broke the previous record of 2.3” that had fallen in 1957. A fairly cold stretch followed through mid-April with temperatures hovering around 10 to 20 degrees below normal. A record low maximum temperature was tied on the 7th then the high temperature could only get up to 32 degrees. The first two-thirds of the month were actually fairly dry with most of the precipitation coming in the day of the snowstorm. This all changed over the last week of the month when the weather pattern became a bit more progressive. Heavy rainfall led to quite a bit of river flooding. Portions of Will and Lake (IN) counties had up to 4 inches of rain over a 3 day period. O’Hare’s rainfall caught up to the monthly normal with this rainfall. There were only two severe events in the region during April. The first severe event was a morning squall line on the 3rd that dropped some ¾” to 1.5” hail. The second event was the weak 5 yard wide tornado/landspout that formed over Plainfield and ended over Bolingbrook and did some very minor damage. Overall, the climate statistics for the month ended up near normal for almost all the categories, with the exception of snowfall, which was double the normal amount. The warmest temperature of the month was 83 degrees which occurred on the 22nd, while the coldest temperature was 22 degrees on the 7th.
The month of May will likely be remembered for how dry, warm and windy it was for most of the month. From the 1st of the month through 23rd, most of the region had received less than an inch of rain. Some much needed rains came toward the end of the month, but most observing sites still ended up with an inch to two inch deficit. Adding Abnormally Dry (DO) drought conditions to northern Illinois was being considered right before the Memorial Day weekend since there had been a lull in precipitation and quite windy conditions to help evapotranspirate moisture from the soil. However, timely rains energized crops and lawns and conditions improved. With the low amounts of moisture, that translated to a quiet severe weather month, with the exception of high wind events on the 15th and 24th. The warmest temperature of the month was 90 degrees on the 14th, while the coldest temperature was 42 on the 2nd and 18th. No records were broken. The average temperature of 63.8 degrees was the 16th warmest on record. For the spring season, it was the 10th warmest on record, but was near normal for precipitation.
June will likely be remembered for being dry…and wet if that is possible. Coming into June, there had been a deficit of an inch to three inches of rainfall from a dry May. Thoughts of a drought dwindled though as the first 6 days of June recorded 0.01” of rainfall or more. However, the next week and a half was dry and we started to ponder again whether or not we were at the beginning stages of a drought. Some scattered storms came in here and there through the next week, but all thoughts were dashed on the 26th when the north side of Chicago about 3 to 5 inches of rain fell within an hour, leaving the north side drenched. Traffic was stranded on Lake Shore Drive as all the exit ramps were flooded. The dugouts at Wrigley Field had to be sandbagged and pumped out, but they were still able to get the game off in the evening. This intense rainfall was limited to the north side of town, as O’Hare ended up being 1.34” below normal for the month…and thoughts of dry conditions linger. No records were set in June, but the highest temperature was 93 on the 16th and the lowest temperature was 44 on the 6th
One of the quietest July’s in recent years as temperatures were almost exactly normal, precipitation was just barely above normal and no records were set during the month. The 9th was an active day for severe weather with flash flooding occurring in the De Kalb area. A microburst in the early morning hours on the 26th also occurred in the Homer Glen/Burr Ridge area. The warmest days of the month were on the 8th and 9th when the high hit 94 degrees and the coldest days of the month was on the 2nd when the low got down to 53 degrees. 
After lingering at or below normal precipitation-wise throughout 2007, the flood gates opened up in August. There were two extended periods of heavy rainfall that lasted a week or longer, one early on in the month and another toward the end of the month. In both situations, a stationary front was present in the region and helped focus the development of thunderstorms across the same region day after day. There were 4 days where over an inch of rain fell, with the highest amount at O’Hare on the 23rd, which set a daily record with 2.35 inches falling.   This was also the day of two squall lines that produced a tornado in Winfield and then produced extensive damage across the Chicago area. The worst flooding was along the Des Plaines River where excess runoff from heavy rain in southern Wisconsin added to the rain that fell in northern Illinois and caused flooding along most of the river basin. There was also a massive supercell thunderstorm that developed in northwest Indiana on August 15th and caused damage from Gary down through Kouts where high tension wires had been toppled. This month of August ranked as the 4th wettest August on Chicago’s record books, while the summer season ended up being the 9th wettest summer ever. The hottest temperature was the 1st when the high touched 92 degrees, while the coldest temperature was on the 30th and 31st when the low dropped to 57.
After such an active month of August, Mother Nature calmed things down for September. Precipitation was pretty much non-existent, but didn’t cause any drought concerns after having a record breaking month of precipitation in August. Most of the region only received around an inch of rain or less for the entire month. For the 5th month in a row, temperatures were above normal. The highest temperatures came on the 5th and 24th when the high got up to 90 degrees. The coldest temperature came on the 15th when it dipped to 39 degrees and broke the previous record. No other records were broken in September. 
The weather highlight from October was probably the big severe weather event that took place across northeastern Illinois and northwest Indiana on the 18th. There was high potential for tornadoes on this day, but luckily it mainly ended up being a hail event from Cook/Will County south and eastward. Other than this severe weather event, the month will be remembered for how warm it was (11th warmest October on record)…almost summer-like. One of the last concerns we at the NWS had going into our Open House on the 6th was that it may be too warm…but that is what ended up happening with highs getting into the upper 80s across the region that day. Two records were broken in October at O’Hare. Both occurred on the 7th when a record high temperature of 87 and a record highest minimum temperature of 67 broke the previous records. The warmest temperature of the month was 87, which occurred on the 6th, 7th, and 8th, while the coldest temperature of the month was 34, which occurred on the morning of the 28th and brought an end to the long growing season. Precipitation was under the norm by about an inch with no really heavy rain days at the airport.
November was a fairly quiet weather month across the region as both precipitation and snowfall was below normal and temperatures were right around normal with no records broken throughout the month. The main weather story was likely the pre-Thanksgiving weather conditions that hampered travel in the days ahead of the holiday. Low cloud bases and low visibility caused major delays at airports across the region, particularly on the Monday and Tuesday before the holiday weekend. A potent storm system then came through on Wednesday night and brought a wet, slushy inch to two inches of snow to northern Illinois right as motorists started to head out for Thanksgiving.   The other main story was how dry the fall was after such a wet summer. With another dry month on the books, the fall season ranked as the 8th driest on record…which followed the 9th wettest summer, so at this point everything seems to be back in balance. The highest temperature of the month occurred on the 12th when it reached 66 degrees, while the coldest temperature was 18 on the 29th.
After a couple quiet months of weather after the wet August, Mother Nature came back with a very active month of winter weather across the region for December. The beginning of the month was filled with an unusually high amount of days with freezing rain as a frontal boundary became stationary across the Ohio River Valley. The 1st of the month was probably the worst of the multiple events with a quarter to a half inch of ice forming across the Chicagoland area. Luckily, temperatures climbed above freezing later that evening which allowed the ice to melt and not cause further problems. The first big snowstorm of the season occurred on the 5th when some portions of far Northeast Illinois received up to 9” of snow when a potent Alberta Clipper dropped through the region.   The next decent snowstorm came through on the 15th into the 16th when portions of southern Cook County into Northwest Indiana received 9 to 12 inches of snow. The snowy conditions would continue off and on for the rest of the month as 17out of the 31 days had at least a Trace of snow at O’Hare, which made this the 13th snowiest December in Chicago’s history. One record was tied in the month with the low temperature dipping down to 0 on the 6th. This was the coldest temperature of the month, with the warmest being on the 23rd when it climbed to 52 degrees.
Tim Halbach
Climate Focal Point
NWS Chicago is the U.S. government's official web portal to all federal, state and local government web resources and services.