March 2012: Unprecedented Early Season Heat

Below is some information from Chicago and Rockford to reflect on the historically warm March of 2012. This includes the incredible stretch between March 14^th and March 23^rd, when summer warmth visited much of the northern tier of the United States and southern Canada, resulting in warm temperature records (high and/or warm low) being broken or tied for 10 consecutive days at both Chicago-O'Hare and Rockford.

Chicago - Records Broken

 Rockford - Records Broken

On Records

Regarding the unprecedented number of 80 degree days in March 2012

• In Chicago...prior to March 2012, there had only been 10 days in March with highs in the 80s, which means on average, Chicago had seen an 80 degree high in March once about every 14 years.  There were 8 days at or above 80 in March 2012, 6 above the previous record of 80 degrees in a March set in 1986. Including the 8 days at or above 80 this March, there have now been a total of 18 March days at or above 80 in Chicago. This means about one third of one percent of all March days have been in the 80s in Chicago. Therefore, 8 of 18 (roughly 44%) of Chicago's 80° days in March, dating back to 1871, occurred in March of 2012!

• The last time Chicago saw an 80 degree temperature during the month of March (prior to 2012) was over 22 years ago back on March 12, 1990, when the high temperature was 81.

• 80° warmth is not very common even in April, let alone mid March. Chicago only averages about 1 day in the 80's in April each year. Only once in the 140 recorded years of weather observations has April produced as many 80° days as have been observed this March. That was set back in 1977, when 8 days peaked at or above 80°. In fact, only 24% of all Mays on record in Chicago have had more than eight 80° degree days!

• In Rockford, prior to March 2012, there had been a total of 12 days in the 80s in March dating back to 1906, which means Rockford averages an 80 degree day in March approximately once every 11 years. There were six days at or above 80 this March. Including those six days at or above 80 this March, there have now been a total of 18 March days at or above 80 in Rockford. This means only about four tenths of one percent of March days in Rockford had high temperatures in the 80s. Therefore, 6 out of 18 (roughly 33%) of Rockford's 80° days in March occurred in March of 2012!

• Prior to this year, the last time Rockford had an 80 degree day in March was on March 26, 2007, when the high temperature was 80.

• In Rockford, 80° warmth is slightly more common in April due to its greater distance from the cooling effects of Lake Michigan. Rockford averages 3 days in the 80's in April. Its record for the highest number of days above 80° was set in April 1915 with 9 days. There have been three April's that have recorded at least 7 days in the 80's. 

A Final Word: More Interesting Facts on the Historic Warmth

Chicago-O’Hare

• In Chicago, the previous warmest March on record occurred in 1910 and then in 1945, which both averaged 48.6 degrees. March 2012 finished with an average temperature of 53.5 degrees, shattering the old record by an astounding 4.9 degrees!. Not only did this shatter the record for the warmest March, it would have ranked as the 7^th warmest April in Chicago! 

• The 4.9 degree difference between the average temperature for March 2012 at Chicago-O'Hare and the previous record for warmest March is by far the largest difference between 1st and 2nd place between record warm or cold months in Chicago. The second largest difference between 1st and 2nd place is the 3.1 degrees separating the average temperature of January 1880 (39.8) and January 1933 (36.7) for the warmest Januarys on record in Chicago.

• The 15.6 degree departure from normal for March 2012 is the 3rd largest departure from the 1981-2010 normal for any month in Chicago. The only months that had higher departures from normal were January 1877, which with an average temperature of 39.8 degrees, was 16 degrees above the 1981-2010 average January temperature, and December 1877, which with an average temperature of 43.4 degrees, was 15.7 degrees above the 1981-2010 average December temperature.

• Chicago-O'Hare's March 2012 average temperature would rank as tied for the 14^th coolest May in Chicago!

Rockford

• In Rockford, the previous warmest March on record was in 1945, with an average temperature of 48.2.  March 2012 finished with an average temperature of 52.4 degrees, shattering the old record set in 1945 by an astounding 4.2 degrees! Not only shatter the record for warmest March, it would have ranked as the 15^th warmest April in Rockford!

• The 4.2 degree difference between the average temperature for March 2012 in Rockford is almost a full degree higher than the second largest difference between 1st or 2nd place for record warm or cold months in Rockford. The second largest difference is the 3.4 degrees separating the average temperature of August 1947 (80.6) and August 1983 (77.2) for the warmest Augusts on record in Rockford.

• The 15.2 degree departure from normal for March 2012 is the 3rd largest departure from the 1981-2010 normal for any month in Rockford. The only months that had higher departures from normal were January 1912, which with an average temperature of 4.7 degrees, was 16.8 degrees below the 1981-2010 average January temperature, and January 1977, which with an average temperature of 5.9 degrees, was 15.6 degrees below the 1981-2010 average January temperature.

• The March 2012 average temperature would have ranked as the 3^rd coolest May in Rockford!

Links to More Information

The Historic March 2012 Heat Wave: A Meteorological Retrospective

March 2012 Review from NOAA ESRL