September this year at the Indianapolis International Airport was the warmest September on record, based on data from the NOAA Regional Climate Center. Records for the Indy airport go back to 1943.
The mean average temperature for September this year was 73.7 degrees Fahrenheit. That’s 2 degrees warmer than the next-warmest September on record, which came in 2007. It’s about 7 degrees warmer than the mean of all September averages since 1943, which is 66.9 degrees.
Last year’s September (2018) ranked 4th warmest since 1943.
Records for Monroe County’s airport go back just a couple of decades. This year’s September numbers are the warmest since 1998 by about a degree—72.1 compared to 71 degrees last year.
Data in the climate center’s database for Indiana University station’s in Bloomington go back to 1896, but temperature data stopped getting reported in late August this year. The Beacon has made some inquiries into that. [Updated Oct. 4, 2019: The word from National Weather Service is: “The IUBloomington station is undergoing some construction so the site is temporarily down. The time table for it being back up and running is unknown due to the construction. But, it will be back.”]
Not counting this year, the warmest September on record for Bloomington came in 1933 with a monthly mean average temperature of 74.5 degrees. If the airport temperature were taken as a proxy for the IU station, this year’s 72.1 degrees would rank as the 10th warmest September since 1896.
Swapping in Monroe County airport numbers would be a tricky business—the monthly averages can differ by as much as 3 degrees compared to the IU station.