September 2011 Climate Summary

Central Indiana

September 2011

Climate Summary


Tied for 55th Coolest on record at Indianapolis

18th Wettest on record at Indianapolis



September began blistering hot across the Ohio Valley as a broad upper level ridge acted as the dominant weather feature.  Temperatures warmed into the upper 90s across much of central Indiana for the first three days of the month, with the temperature officially reaching 100 degrees at the Indianapolis International Airport on the 3rd.  This marked the first time the temperature had made it to the century mark at Indianapolis in September since September 5, 1954. The 100 degree high was a record high temperature for the date. The temperature reached or exceeded 99 degrees at Indianapolis September 1-3, marking the first time this had happened for three consecutive days since July 1988.  The only time this has occurred later in the calendar year was September 13-15, 1939. 


The passage of a cold front and arrival of the remnants of Tropical Storm Lee brought an extended period of cloudy, cool and damp weather to much of the Ohio Valley beginning on the 5th and persisting through the 9th as high temperatures largely remained in the lower and middle 60s.  This was a sudden and abrupt change from the hot temperatures to start the month, as average temperatures during this period were 20 to 25 degrees cooler than those experienced from the 1st through the 3rd.  Temperatures warmed back to above normal levels with the departure of Lee’s remnants, with the warmest high temperatures experienced on the 12th and 13th as temperatures rose into the upper 80s and lower 90s. At Indianapolis, the high temperature of 92 degrees on September 13th marked the 42nd day in 2011 that temperatures had reached or exceeded 90 degrees.  This made for the most days at or above 90 degrees in a calendar year since 1988, when the mercury reached 90 in Indianapolis on 49 days.


Temperatures turned cooler once again on the 14th with the passage of a cold front.  Highs fell back into the 60s in the days to follow, with lows falling into the 40s for many for the first time in the fall on the 15th and 16th. Some locations across northeast portions of central Indiana dropped into the upper 30s on the morning of the 16th.  Temperatures returned to near normal from the 17th through the 22nd, before cooler weather intervened once again beginning on the 23rd as a stubborn and very slow moving upper level low impacted the region through the 28th with cloudy, cool and unsettled weather. Many locations across central Indiana were unable to rise out of the 50s on the 25th as rain fell for much of the day. Highs returned to the mid and upper 70s for one day on the 29th, before a cold front brought colder weather in for the 30th continuing into early October.



September 2011 Avg Temp

September 2011 Difference from Normal



Lowest Temperature




100 on 3

45 on 16




98 on 2

42 on 15




94 on 2 and 3

39 on 16

Terre Haute



98 on 2 and 3

43 on 16




99 on 3

41 on 16




98 on 3

38 on 16

Indy – Eagle Crk.



97 on 2 and 3

43 on 16


At Indianapolis, 16 days had below normal average temperatures, 12 days experienced below normal average temperatures, and 2 days experienced normal average temperatures.


September 2011 was tied for the 55th coolest in the Indianapolis area since 1871.




Normal to much above normal September monthly rainfall abruptly ended the summer drought in much of central and southern Indiana.   Monthly rainfall ranged from slightly over 2 inches in extreme west central Indiana to more than 9 inches in portions of southwest Indiana near the Ohio River.  Much of the state received 3 to 6 inches of rainfall during September.  At the Indianapolis airport 5.37 inches of rain fell during the month...the most for September since the record wet September of 2003.

Almost all of the rainfall during the month fell after the 10th.  A large share of the rainfall in central and southern Indiana occurred from the 19th through the 25th.   A storm system moving through the region on the 19th produced much needed rainfall across most of central Indiana.  Some of the heaviest rainfall fell across northern portions of the Indianapolis metro area, with many locations receiving 2 to 3.5 inches.  At the Indianapolis International Airport, this was the highest daily rainfall since June 20.

A slow moving low pressure system moving across the Ohio Valley on the 24th and 25th produced a widespread 1 to 3 inches of rain across much of central Indiana.  The heaviest rain fell during the afternoon and evening of the 25th from near Vincennes northeast through Bloomington and Indianapolis, where many locations received in excess of 2 inches of rainfall. The 2.17 inches of rain on the 25th at Indianapolis was a record rainfall total for the date. The only area remaining quite dry was a small portion of west central Indiana composing of Vermillion and Warren Counties between the Wabash River and the Indiana-Illinois state line.



September 2011 Precipitation

September 2011 Difference from Normal

Wettest Day

Longest Dry Stretch




2.17 on 25

3 days 1-3




0.82 on 25

2 days 1-2, 5-6, 12-13, 15-16, 20-21




1.09 on 25

2 days 1-2, 5-6, 12-13, 16-17

Terre Haute



1.46 on 25

3 days 1-3 and 5-7




2.14 on 25

2 days 1-2 and 5-6




1.88 on 11

2 days 1-2 and 20-21

Indy – Eagle Crk.



2.86 on 19

6 days 1-6


September 2011 was the 18th wettest in the Indianapolis area since weather records began in 1871.


Severe Weather


Scattered strong to severe thunderstorms occurred ahead of a cold front during the late afternoon and evening of the 3rd.  The storms primarily produced damaging winds from the Indianapolis metro area northeast to Anderson and Muncie.  An EF1 tornado occurred in Jennings County early on the morning of the 26th as low pressure moved through the region and triggered a few severe thunderstorms across southeast and east central Indiana.


For information on severe weather in other areas during September, visit the Storm Prediction Center “Severe Weather Event Summaries” website at




The maximum wind gust at the Indianapolis International Airport was 45 mph from the northwest on the 29th as a line of showers and thunderstorms arrived. Fog or haze was reported at Indianapolis on 19 days this month. Thunder was reported at Indianapolis on 6 days this month.


October 2011 Outlook


The official outlook for October 2011 from the Climate Prediction Center indicates a greater chance for above normal temperatures across central Indiana, and equal chances of below, above, or normal precipitation.   At Indianapolis, the average temperature for the month is 55.0 degrees.  The average precipitation for October at Indianapolis is 3.12”.  


Data prepared by the Indianapolis Forecast Office.


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