2011 Summer Roundup

This meteorological summer was quite the rollercoaster ride.  The start of it included some cooler temperatures, quickly followed by temperatures above 90°F.  Towards the end of June we endured some severe weather, and for the majority of July we saw very little rain.  Toward the end of July, the large amplified ridge, which had been the result of a Ring of Fire pattern, shifted somewhat south.  As a result, Chicago O’Hare International AP received record amounts of rain.  July 2011 quickly became the wettest July on record, after it started out as one of the driest.  August brought a bit of reprieve in terms of temperatures. And, although northern IL received quite a bit of rain, other areas around the region were not so fortunate with areas south of I-80 remaining drier than normal.


So, how does this meteorological summer compare to others?


In the past 30 years, the average number of 90°F days for the Chicago area was 14.6 days.  This summer ran slightly above average, thanks to July.  O’Hare received 19 days in which it was 90°F.  63% of this summer’s 90°F days occurred in July.  This may be slightly/higher than other observation stations within the CWA due to effects such as:  the urban heat island, geography, or equipment.  Similar to temperature, precipitation amounts were also above average.  The average amount of precipitation over this three month period is 12.07”.  This year we received 19.08” of precipitation, of which 58% occurred in the month of July (11.15”).


If a comparison was done of based on the average summer high temperatures over the past 30 years, this summer would be the 2nd warmest since 2005.  Below is a graph comparing the past 30 years:

Overall this summer turned out to be slightly above average in terms of temperature.  The normal average for this three month period is 82°F.  For the summer of 2011, the average summer temperature was 83.5°F.  The month of July was the warmest of the season, and contributed the most to our above average temperature.  The warmest meteorological summer in the past 30 years was 1988, where we had an average summer temperature of 87.2°F. 

Jeff Kilburg

Senior Meteorology Student - Northern Illinois University

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