Sunday, August 2, 2009

July '09 is Coldest in 60 Years

From the NWS in Indianapolis
Central Indiana July 2009 Climate Summary

July 2009 was the coolest in more than 60 years for much of Central Indiana. Average monthly temperatures were 3½ to 6 ½ degrees below normal. July’s average temperature was 2 to 4 degrees cooler than June. During July above normal rainfall continued in many areas south of Indianapolis. A dry trend developed in many areas north of Indianapolis. Rain events were rather evenly distributed during July, with rain occurring about every 7 days. A persistent trough of low pressure across eastern Canada and the Eastern United States helped funnel cool Canadian air into the Ohio Valley for much of July.

The following is a summary of the weather in Central Indiana during July 2009.


July 2009 featured little summer heat in Central Indiana and record to near record cool monthly average temperatures. The month began with temperatures well below normal and this trend continued nearly uninterrupted the entire month. The only first order station to report 90 degrees in central Indiana was Muncie.

At Indianapolis, July’s average temperature of 70.9 degrees was the second coolest of record and the lowest since 1947. July’s average temperature was only 0.3 of a degree higher than in 1947. This was similar to the normal July temperature at Lansing, Michigan.

The average maximum temperature of 79 degrees at Indianapolis was the lowest of record breaking the previous record low average maximum of 81 set exactly 100 years ago. This is the first July of record with an average maximum temperature of less than 80 degrees.

Another unusual climate feature at Indianapolis was July’s average temperature was 2.5 degrees lower than in June. This was only the 9th time since 1871 that the average temperature for July was cooler than June. The last time this occurred was in 1984. The greatest difference was in 1971 when July was 3.4 degrees cooler than June. Typically the average temperature increases 3.7 degrees from June to July.

Other temperature features at Indianapolis include:

·All of July’s daily average temperatures were below normal except for the 10th, 28th and 29th.

·The temperature failed to reach 90 degrees in July for the first time since 2004. This is the 9th July since 1871 to not reach 90 degrees. Typically 7 days in July reach 90 degrees.

·Only 3 days with a temperature of 85 degrees or higher. This has never happened since weather records began in 1871. The previous record was 7 days set in 1875.

·14 days did not reach 80 degrees. The average is 5. The previous record of 12 occurred in 1909 and 1915.

·Record Low Maximum Temperatures were set on the 4th, 18th and 22nd. On the 1st, the high temperature of 69 was the second lowest of record for the date and missed tying the record set in 1924 by 1 degree. For the 4th the new record is 70 degrees breaking the previous record of 71 set in 2008. For the 18th the new record is 71 degrees breaking the previous record of 75 first set in 1871 and repeated in 1883. For the 22nd the new record is 68 degrees breaking the previous record of 70 set in 1996.


July 2009 was a wet month across much of southern Indiana and a rather dry month for areas immediately north of Indianapolis. Monthly rainfall of 5 to 10 or more inches occurred in most areas south of I-65 west of Indianapolis and south of I-70 east of Indianapolis. North of this area and south of US 24 generally 1 to 3 inches of rain fell during July. The biggest rain during July occurred in south central Indiana where nearly 5 inches fell on July 22nd.

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