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| County temperatures derived from ISU observations (www.pals.iastate.edu/campbell) by grid-interpolation. |
| Risk of nitrogen loss is reduced when soil temperatures are continuously below 50F. |
Dates during the past few years when the soil temperature cooled to below 50F for various spots in Iowa: |
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- 2008-- Statewide soil temperature cooled to below 50F on November 7.
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- 2007-- Soils North of a line from Council Bluffs to Waterloo and then directly East cooled to below 50F on November 1st and statewide on November 13th.
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- 2006-- Soils in the northwest 10 counties of Iowa cooled to below 50F on November 9th and state wide on November 29th.
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- 2005--Soils in the northwest 9 counties of Iowa cooled to below 50F on October 30 and statewide on November 12th.
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- 2004--State-wide soil temperature cooled to below 50F on Nov. 21st.
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- 2003--Iowa soils cooled to below 50F by Oct., 28th. However, a warming impacted the areas south of Highway 20. Soils south of Hwy. 20 did not remain consistantly below 50F until Nov. 21st.
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- 2002--Entire state soil temperature below 50F: October 22
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- October 13 Nashua, Ames
- October 15 Sutherland
- October 16 Castana
- October 17 Crawfordsville
- October 19 Lewis
- October 22 Chariton
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- 2001--November 21 average--soil temperature fell below 50F:
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- November 18 in NW Iowa
- November 26 all other locations except the Burlington area
- November 30 Burlington area
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- 2000--November 3 (Kanawha, Nashua, and Ames)
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| E. Taylor, Climatologist |
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