A Cold, Wet October

Pat Guinan
State Climatologist
Commercial Agriculture/University of Missouri Extension

October 2009 will go down as one of the Top 5 wettest and coolest Octobers on record for Missouri (Figure 1). Preliminary numbers, at the end of the month, indicate statewide temperatures averaged about 6 degrees below normal with nearly three times the normal rainfall. Some locations witnessed their wettest October in more than a century. St. Louis, MO recorded their wettest October on record, with 12.38 inches officially tallied at Lambert International Airport. That's an amazing statistic considering St. Louis has precipitation records that extend back 137 years.

Initial October rainfall reports indicate October 2009 will rank as the second wettest October on record for Missouri. Officially, October 1941 ranks as the wettest October on record for the Show Me state, with an average statewide total of 10.47 inches. Preliminary numbers for 2009 are indicating a statewide average of just over 10 inches. Regionally, lighter amounts, in the 4-7" range, were reported across northwestern sections but these totals were offset by heavier amounts, in excess of a foot, across several east central and southeastern counties. A few Ozark observers, from Shannon and Oregon counties, reported more than 15 inches of rain during October. It will be close in regard to breaking the 1941 record, but it's safe to say most Missourians witnessed the wettest October in nearly 70 years.

Temperatures for the month were much below normal and preliminary numbers are indicating 2009 will rank between the 3rd and 5th coolest October on record, and the coolest October in more than 30 years. A very active weather pattern during the month led to frequent rain events and extended cloudy periods. These conditions, combined with cool temperatures, minimized evaporation rates and resulted in persistent, wet soils across Missouri. Similar weather conditions were reported across much of the Midwest, as well as a growing concern for major harvest delays. Crop harvest was running several weeks behind normal across the region and the extreme wetness was creating other problems related to crop disease, grain dry down, stalk lodging, winter wheat planting, compaction, and fieldwork preparation for next year.

Figure 1.

Top 5 Wettest Octobers Top 5 Coolest Octobers
Missouri Missouri
Year Precip. (in.) YearAvg. Temp. (F)
194110.47 192547.8
2009*10.17* 191749.1
19197.23 197650.5
19847.17 189550.5
19676.61 2009*50.6*

*Preliminary
Period of Record: 1895-2009