WFO Chicago

2007 Climate Summary for Rockford
                                

Temperature                                                          Precipitation

Month
High
Low
Average
Departure
Total
Departure
Snow
Departure
January
33.1º
18.5º
25.8º
+6.8º
0.81”
-0.60”
7.5”
-2.8”
February
23.5º
8.3º
15.9º
-8.8º
1.43”
+0.09”
14.9”
+7.0”
March
51.8º
33.2º
42.5º
+6.4º
3.25”
+0.86”
1.3”
-4.3”
April
57.7º
36.8º
47.3º
-0.6º
2.73”
-0.89”
2.9”
+1.5”
May
77.8º
52.0º
64.9º
+5.3º
1.25”
-2.78”
0.0”
0.0”
June
81.6º
60.0º
70.8º
+2.0º
4.07”
-0.73”
0.0”
0.0”
July
84.6º
61.8º
73.2º
+0.3º
2.43”
-1.67”
0.0”
0.0”
August
83.8º
65.3º
74.6º
+3.7º
13.98”
+9.77”
0.0”
0.0”
September
80.0º
53.9º
66.9º
+4.1º
2.04”
-1.43”
0.0”
0.0”
October
69.1º
47.8º
58.5º
+7.5º
1.44”
-1.13”
0.0”
-0.1”
November
47.2º
29.3º
38.3º
+1.1º
0.40”
-2.23”
1.0”
-1.6”
December
31.4º
18.7º
25.0º
+0.6º
3.28”
+1.22”
21.7”
+10.9
Total/Ave
60.1º
40.5º
50.3º
+2.7º
37.11”
+0.48”
49.3”
+10.6”

 
Yearly Extremes:
 
Highest Temperature:
 93 on June 16th and July 8th
 
Lowest Temperature:
 -13 on February 5th and February 6th
 
Most Precipitation in One Day:
 5.15” on August 7th
 
Most Snowfall in One Day:
 5.2” on December 28th
 
 
 
Records set during 2007:
 
           
Temperatures:
           
            Highs:
March 13th (74)
March 25th (79)
May 14th (92)
September 24th (92t)
October 7th (88t)
 
            Lows:
None
 
            Highest Lows:
March 26th (62)
October 6th (67)
October 7th (67)
 
            Lowest Highs:          
August 18th (65)
 
            Monthly:
16th Warmest September
5th Warmest October
 
            Seasonal:
None
 
Yearly:
13th Warmest Year
 
 
Precipitation:
           
            One Day Precipitation:
August 7th (5.15”)

            Monthly Precipitation:
Wettest August on Record (13.98”)
Wettest Month on Record (August, 13.98”)
3rd Driest November (0.40”)
 
Seasonal Precipitation:
6th Wettest Summer (20.48”)
7th Driest Fall (3.88”)
 
            One Day Snowfall:
April 11th (1.9”)
April 12th (1.0”)
November 21st (1.0”t)
 
            Monthly Snowfall:
6th Snowiest December (21.7”)
 
            Seasonal Snowfall:
None
 
            Yearly:
36th Wettest Year
 
 
 
JANUARY
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 7 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 that much accumulation with 7.5 inches of accumulation for the month. The warmest temperature of the month was 51 degrees on the 4th and 5th and the coldest temperature was -2 on the 17th.
 
FEBRUARY
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 a decent amount of snowfall as well, with 14.9” inches falling, which ended up being almost the same amount that had previously fallen through the entire season up to February. No records were set during the month of February, which was the second month in a row without a record being set. The warmest temperature of the month was 48 on the 21st, while the coldest temperatures were on the 5th and 6th when it dipped down to -13.
 
MARCH
It has been a tale of three completely different months so far in 2007. January had quite a few days of light snow, but was above average for temperatures. February was very cold with a lot of snow. Then March came along and ended up being the 8th warmest March on record. Three high temperature records were broken during the month. The warmest temperature of the month was on the 26th when the temperature reached 80, while the coldest temperature of the month was 13 on the 6th.
 
APRIL
Going into April, the region had been spoiled with temperatures in the 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 1.9 inches of snow that fell on the 11th and the 1.0” that fell on the 12th broke the previous records of 0.8” that had fallen in on each day in 1973 and 1962 respectively. A fairly cold stretch followed through mid-April with temperatures hovering around 10 to 20 degrees below normal. The first two-thirds of the month were actually fairly dry with most of the precipitation coming on 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 further south and east of the Rockford area, with the monthly total at Rockford ending up about an inch below normal. 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. Climatologically, temperature stats were very normal, with precipitation being almost an inch below normal and snowfall being about double the normal value. The warmest temperatures of the month was 84 on the 22nd and 29th, while the coldest temperature was 20 on the 6th.
 
MAY
The month of May will likely be remembered for how dry 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 came and 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 92 degrees on the 14th (which was a record high for the day), while the coldest temperature was 39 on the 18th. The average temperature of 64.9 degrees for May was the 8th warmest on record and the 1.25” was the 5th driest. For spring, it was the 5th warmest and 17th driest on record.
 
JUNE
Overall, the month of June ended up being fairly normal weather-wise for Rockford, aside from a few severe weather events. The average temperature ended up being a few degrees above normal, but precipitation ended up being a little below normal and no records were set. The first severe weather event was on the 1st when severe winds knocked down power lines and trees across north central Illinois. One person was injured in Sandwich at the Relay for Life event when some shelters blew over. The warmest temperature was 93 on the 16th, while the coldest temperature was 48 on the 6th.
 
JULY
A somewhat quiet month in the Rockford area as temperatures were right around normal, but precipitation was lacking and ended up over an inch and a half below normal. However, on the 9th there was flash flooding that occurred in the DeKalb region as thunderstorms trained over the same places. About 4 to 5 inches of rain was reported, and the flooding that resulted led to the evacuation of some dorms at NIU as well as water rescues for people stranded in their cars. This flooding was a sign of things to come in the next month. The warmest day of the month was on the 8th when the high hit 93 degrees and the coldest day was on the 13th when the low got down to 53 degrees. 
 
AUGUST
August of 2007 went down in the record books as being the wettest month in Rockford’s 102 year weather history with 13.98 inches of rain falling throughout the month. From August 4th through August 25th there were only 4 days that did not record a measurable amount of precipitation. There were 4 days where over an inch of rain fell, in particular the 7th and the 19th. On the 7th, 5.15” of rain fell, which was a daily record for that day. Numerous other recording sites around the Rockford area reported over 6 inches of rain. While flash flooding was bad in August of 2006, that was over a small area in the city of Rockford. The flooding of August 2007 was way more widespread across most of northern Illinois along the Wisconsin border. As the rain continued, the rivers began to swell up. Combined with the heavy rainfall in southern Wisconsin at the upstream portions of the Rock, Pecatonica and Kishwaukee rivers reached bankful stage and flooding rapidly occurred along these rivers. As for temperatures, with the extra moisture in the air, low temperatures overnight didn’t drop a whole lot. The high temperatures of 65 on the 18th broke the lowest high temperature record for that date. The hottest temperature recorded was on the 2nd when it reached 92, while the coldest temperature was 54 on the 31st.
 
SEPTEMBER
After all the flooding and record rainfall in August, Mother Nature relaxed in September and allowed for a nice drying period. For a two week stretch in the middle of the month, there wasn’t a drop of rain in Rockford, which allowed all of the rivers to go back down to their normal levels. For the month, Rockford ended an inch below normal for rainfall. The average temperature was again above normal for the 5th month in a row, and the 7th out of 9 months this year that have been above normal. The highest temperature of the month was on the 24th when the high temperature reached 92 degrees and tied a record for the day. The lowest temperature of the month was on the 15th when the temperature dipped to 35 degrees…the first time since May that the temperature had gone into the 30s.
 
OCTOBER
The month of October in Rockford had people thinking that it was the middle of summer again, particularly at the beginning of the month when the high temperature was 83 or higher on five straight days. Overall, the month ended up being the 5th warmest October on record, which continued the streak of above normal months in a row to six. There wasn’t much to speak of for severe weather in the Rockford area in October as the big severe weather event of the 18th stayed mainly in the Chicago area. Three records were broken or tied during the month. The first was on the 6th when a record high minimum temperature of 67 degrees occurred. The second and third both occurred on the 7th when the high temperature of 88 tied the previous record and the minimum temperature of 67 broke the highest minimum record. The warmest temperature of the month was on the 6th and 7th when the high tagged 88, while the coldest temperature of the month was on the 28th when it got down to 30 degrees. This was the first freezing temperature at Rockford since mid-April and essentially ended the extended growing season. Precipitation was a little over an inch under normal for the month with no real heavy rain at all.
 
NOVEMBER
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 1.0 inch of snow that fell on the 21st tied a record for most snowfall on that day. The other main story was the how dry fall was compared to the summer and particularly August. After the 6th wettest summer, fall ended up being the 7th driest fall on record, with this November being the 3rd driest November on record…so at this point everything seems to be back in balance precipitation wise. As for temperatures, with another above normal month on the books, it made for the 7th month in a row that was above normal. The highest temperature of the month occurred on the 12th when it reached 65 degrees, while the coldest temperature was 15 on the 30th.
 
DECEMBER
After a few months of quiet weather, December took it up a notch as a frontal boundary stalled out across the Ohio River Valley and caused multiple episodes of freezing rain. The worst event was on the first of the month where about a half inch up to three quarters of an inch of ice accumulation occurred across portions of the Rockford area. Over the next two weeks, there would be three more days of freezing rain or drizzle across north central Illinois until the stationary front finally moved off to the east coast. The rest of the month was rather snowy as colder air moved in across the region. There were only 9 days out of the month that did not register at least a Trace of snowfall. The heaviest snowfall for North Central Illinois was on the 28th when 4 to 7 inches of snow fell across the region. The 21.7 inches of snow that fell was the 6th snowiest on record and more than doubled the norm. The warmest temperature of the month was on the 23rd when it climbed to 47 degrees (then proceeded to drop to 11 by the end of the night), while the coldest temperature was on the 6th when it dipped down to -4 degrees.
 
Tim Halbach
Climate Focal Point
NWS Chicago

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