WFO Chicago

2006 CLIMATE SUMMARY FOR CHICAGO
                            

Temperature                                                          Precipitation
Month
High
Low
Average
Departure
Total
Departure
Snow
Departure
January
42.0˚
29.6˚
35.8˚
+13.8˚
2.78”
+1.03”
5.5”
-5.8”
February
36.3˚
20.0˚
28.2˚
+1.2˚
1.80”
+0.17”
2.5”
-5.8”
March
46.7˚
29.9˚
38.3˚
+1.0˚
2.70”
+0.05”
5.7”
-0.3”
April
64.1˚
42.1˚
53.1˚
+5.3˚
3.59”
-0.09”
T
-1.6”
May
69.7˚
49.5˚
59.6˚
+0.9˚
3.65”
+0.27”
0.0”
0.0”
June
78.8˚
57.8˚
68.3˚
+0.1˚
4.05”
+0.42”
0.0”
0.0”
July
85.7˚
67.3˚
76.5˚
+3.2˚
3.70”
+0.19”
0.0”
0.0”
August
83.0˚
65.6˚
74.3˚
+2.6˚
2.95”
-1.67”
0.0”
0.0”
September
71.1˚
53.7˚
62.4˚
-1.4˚
5.85”
+2.58”
0.0”
0.0”
October
57.5˚
40.4˚
49.0˚
-3.1˚
4.04”
+1.33”
0.3”
0.0”
November
50.2˚
35.5˚
42.9˚
+3.6˚
3.61”
+0.60”
0.4”
-1.4”
December
40.5˚
27.1˚
33.8˚
+6.4˚
3.18”
+0.75”
5.8”
-2.9”
Total/Ave
60.6˚
43.4˚
52.0˚
+2.9˚
41.90”
+5.63”
20.2”
-17.8”
 

Yearly Extremes:

 
Highest Temperature:
99 degrees on July 31st & August 1st
 
Lowest Temperature:
-7 degrees on February 18th
 
Most Precipitation in One Day:
2.05” on July 20th
 
Most Snowfall in One Day:
5.8” on December 1st
 
Records set during 2006:
 
Temperatures:
 
            Max:
July 31st (99 Tie)   
 
            Min:                             
April 26th (27)
May 22nd (36)
 
            Highest Min:
May 28th (74)
August 1st (80)
November 27th (52)
November 28th (54)
December 31st (43 Tie)
 
            Lowest Max:   
December 3rd (15)
 
            Monthly:
3rd Warmest January
9th Warmest April
11th Coldest October
 
            Seasonal:
None
 
Yearly:
10th Warmest (52.0)
 
Precipitation:
 
            One Day Precipitation:
September 22nd (1.73”)
October 2nd (1.39”)
November 29th (1.73”)
December 1st (1.23”)
December 22nd (0.90”)
 
            Monthly Precipitation:
14th Wettest September (5.85”)
 
Seasonal Precipitation:
12th Wettest Fall (12.50”)
 
            One Day Snowfall:
October 12th (0.3”)-Earliest Measurable Snow in Chicago History
 
Monthly Snowfall:
None
 
            Seasonal Snowfall:
None
 
            Yearly:
18th Wettest Year (41.90”)
 
JANUARY
The year started off very warm and ended up being the 3rd warmest January in Chicago’s history. Every day for the month ended up above normal for the average temperature. Of note was the unseasonably warm overnight temperatures as the minimum temperature rarely even got into the teens (only twice all month). The average temperature for the month ended up being about 14 degrees above the norm for January. The main precipitation event of the month occurred on January 20th when a developing system created an intense band of snow and thundersnow. Snowfall rates were very high and most of the snow fell within a 6 hour period during the evening hours. Some stations reported 13 inches of snow in 6 hours. The line between snow and rain pretty much split the region, as most of the northeastern counties in Illinois had rain/sleet/snow mix through most of the early portion of the event and ended up with a few inches. O’Hare officially ended up with 4.1” of snow for the event. On the whole, precipitation for the month was above normal for the first time since February 2005!
 
FEBRUARY
February was the month where all the storm systems seemed to go to our north, leaving the region without much snowfall to speak of. The most notable case was on the 16th where a frontal boundary set up just to the south of the region. Severe weather was reported in the area, with a possible tornado touchdown in Iroquois county (Wisconsin had thundersnow and blizzard conditions on this day). After this event, high pressure settled in for the rest of the month and created dry conditions. The average temperature and precipitation amount for the month was right around average, but snowfall was once again below normal. The highest temperature for the month was 56 degrees on Valentine’s Day.
 
MARCH
The month of March was pretty much as average as you can get. The average maximum temperature was 0.6 degrees above normal, the average minimum temperature was 1.4 degrees above normal, the average temperature was 1.0 inches above normal, precipitation was 0.05” above normal and snowfall was -0.3 inches below normal. There was a severe weather event on Sunday, March 12th. Quite a bit of hail was reported with this system and some damage was reported in the Bridgeview area which may have been caused by a microburst. With the near normal precipitation conditions and no snow pack to melt, the drought continues on for most of northern Illinois. The highest temperature for the month was 70 degrees on the 30th and the lowest was 20 on the 3rd and 7th.
 
 
APRIL
April was a fairly warm month (9th warmest ever) with quite an active severe weather pattern. The main severe weather events occurred on the 2nd (mainly a hail event, with a few reports of damage from winds and F0 tornadoes), the 13th into the 14th (large hail) and Easter Sunday (a few Tornadoes). There was also substantial flooding with the storms on Easter with some reports of 3 to 5 inches or more in some areas. Rainfall totals for the month were right around normal, helping to improve drought conditions as this was the 4th straight month with totals at or above normal. Chicago was dropped from D2 severe drought conditions down to D0 which means abnormally dry. A record low was set at Chicago with 27 on the morning of the 26th.
 
MAY
Temperature and precipitation wise, May ended up being a very normal month. A cut-off low pressure system was stuck in the western Great Lakes for about a week and a half and created quite a cool streak during the middle part of the month. It also created a bit of wet streak, as there was precipitation of 0.01” or more on 9 days in a row. This was good for the 5th longest record in Chicago’s history for any time period. Even though there were a lot of days with rain, the amounts tended to be small. As the low moved on, the atmosphere went back toward normal and beyond. The warmest temperature of the month occurred on the 28th with a high of 92. A record high minimum was also set on the 28th with a low of 74. There were a few severe episodes, mainly with pulse thunderstorms. One tornado occurred in Kankakee County, 3 miles south of Aroma Park and was rated an F1. Flooding also occurred in most of the counties in northern Illinois on the 24th, 29th, and 30th.
 
JUNE
As was the case in May, June was a very normal month for temperatures and precipitation. The average temperature for the month was 0.1 degrees above normal and precipitation was 0.42” above normal. There were a few severe thunderstorm events on the 2nd, 17th, 19th, 21st and 26th. Probably the most notable event of the month was a heavy rain event that occurred during the overnight hours of the 25th into the 26th. The observer at Midway 3SW reported 1.15” of rain in 15 minutes. There were no tornadoes that occurred during June and no records were broken. The warmest temperature of the month was 92 degrees on the17th and the coldest temperature was 48 degrees on the 5th. The most precipitation in one day occurred on the 10th when 1.58” fell (1.66” fell from the 25th thru the 26th).
 
JULY
The main weather story in July was the two heat waves that we went through. The first wave of 90+ temperatures occurred from about the 13th through the 17th. The warmest day during this period was the 15th when the high got to 97 and the low only fell to 74. The second heat wave was longer and lasted into August. The warmest part of this heat wave came on the 31st into the 1st where a maximum temperature record was tied on the 31st (99 degrees) and a high minimum temperature was tied on Aug 1st (80 degrees).   With the warm weather, severe winds were prevalent whenever a cold front would push through to cool things off. There were no tornadoes during July, but on the 27th there were some funnel clouds that occurred in Will County. There was also quite a bit of heavy rain in Will County on the 27th with some reports of 5.50” of rain in 90 minutes. On the 30th, a few storms rolled through the Chicago Harbor and knocked over 7 sailboats participating in a race.
 
AUGUST
The beginning of August brought the end of the 2nd heat wave in the region. A record high minimum was set on 1st of 80 degrees. An 80 degree minimum temperature is a rarity in Chicago as we average about one every 5 years. The last 80 degree minimum occurred on July 14th, 1995. A squall line went through early in the morning on the 3rd that created quite a bit of tree damage from Lee County all the way to downtown Chicago. After the heat wave ended, temperatures returned to being more normal, but precipitation was scarce as there was a deficit of 1.67”.   This was the largest deficit since the 2005 drought. The highest temperature of the month occurred on the 1st (99 degrees) and the lowest temperature occurred on the 21st (55 degrees).
 
SEPTEMBER
This September was the 14th wettest September on record for Chicago. The main weather story for the month was the flooding that occurred on the 13th. Southern Cook county and Lake county Indiana received about 3-4 inches of rainfall, with portions of Highland, Indiana getting up to almost 8 inches of rain. Most of this fell in about a 3-5 hour period in the morning. About 10 people had basements collapse with many more with water standing in their basement. Flooded viaducts around the south side of Chicago stranded motorists that tried to drive through it. A close call also happened on the 22nd when three distinct supercell thunderstorms developed in northern Illinois and tracked through northern Cook County. A tornado was confirmed with one storm that went through the campus of Loyola University and over Lake Michigan. Numerous hail and wind damage reports came from these and other storms throughout the day. A record amount of rain fell at O’Hare on this day as well, with 1.73 inches falling. Temperatures were below normal for the month for the first time in 2006.
 
 
OCTOBER
The 4th of October was one of the largest warned severe weather events in the history of the National Weather Service in Romeoville. About 43 severe thunderstorm or tornado warnings were issued with almost all of them verified with hail or wind damage. The day began with a cluster of storms moving eastward across northeastern Illinois into northwestern Indiana. As these storms were weakening and moving east, a mesoscale convective system in southern Wisconsin quickly developed and left a swath of damage from the Wisconsin/Illinois border southward all the way through the NWS’s county warning area that extends to Iroquois, Ford, and Livingston counties. One of the hardest hit areas was southern Cook County in the towns of Hickory Hills (where a roof was blown off of a school gym and toppled a service van), Palos Hills and Bridgeview. Two records were set during the month. The first was for the most precipitation for the 2nd with 1.39 inches at O’Hare. The second was for the earliest measurable snow in Chicago’s history. 0.3” of snow fell on the 12th, which also broke the record for the most snow on that day. The average temperature for the month of 49.0 was the 11th coldest, which has continued from the September trend of being cold despite the fact that El Nino conditions exist in the eastern tropics of the Pacific, which tends to lead towards warmer temperatures.
 
NOVEMBER
The month of November was a month of extremes…kind of. While temperatures were below normal for most of the month, a warm spell at the end of the month, that lead to two highest minimum records being broken on the 27th and 28th, caused the average temperatures to be right around normal. There was a stretch in the middle part of the month where the high temperature was in the 40s for 12 days in a row. As for precipitation, there were two days when over an inch of rain fell (10th and 29th) which accounted for most of the rain for the month. The rainfall on the 29th was a record for that day. There were two days of snow during the month: a trace on the 10th on the backside of a cold front and on the 30th when 0.4” fell before midnight with the first big snowfall of the season. Most of that snow fell on the 1st of December. 
 
DECEMBER
December 2006 had a lot of similarities to December 2005 due to a snowstorm in the beginning part of the month, followed by a cold spell for about a week and a half, followed by above normal temperatures the rest of the month. The heaviest snowfall of the year came on the 1st when a swath of 6-13 inches of snow fell across northern Illinois. The snow fell mainly during the morning rush hour on that Friday, but due to the advance warning, most people took off from work or had school cancelled in advance. This Christmas was once again not white, but above normal for temperatures again with no snow cover left from the early snowstorm. Four records were broken during the month: Lowest Max on the 3rd, most precipitation on the 1st and 22nd, and High Min tied on the 31st.
 
Tim Halbach
Climate Focal Point
NWS Chicago

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