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Climatology Bureau


General Summary.   Temperatures over the past year averaged 45.9º or 1.9º below normal while precipitation totaled 43.62 inches or 9.54 inches above normal.   This ranks as the 14th coolest and 4th wettest year among 136 years of state records.   The last cooler year came in 1996 while only 1993 (48.22”), 1881 (44.16”) and 1902 (44.04”) brought more precipitation.   The previous year of 2007 now ranks fifth wettest year (43.35”).

Temperatures.   Cooler than normal weather was the rule for most of the year as only September and November recorded above normal temperatures.   Annual temperature extremes ranged from a low of -30º at Stanley on January 24 to a high of 100º at Hawarden on August 3.   Wind chill indices dipped to -45º at Estherville and Spencer on February 20th, Iowa’s lowest wind chill since January 10, 1997.   Several northeastern Iowa locations never reached 90º during the year while statewide there was an average of only five days with temperatures reaching to 90º or higher.   Only in 1915 and 1992 have fewer 90º days been recorded.   However, despite the persistent cool weather the first hard freeze of the fall came unusually late over most of Iowa.   This was welcome news for crops that were far behind in maturity owing to late planting and early season cool weather.   A few northeast Iowa locations recorded a hard freeze on October 4 and 18 but most of the northwestern two-thirds of the state avoided a killing freeze until October 21 while the growing season extended to October 28 over much of southeast Iowa.

Precipitation.   Iowa came into 2008 with saturated soils and high river levels owing to a very wet last five months in 2007 (wettest August ever, 4th wettest October and 2nd wettest December).   A long cold and wet winter in 2007-2008, followed by a cool and wet spring set the stage for catastrophic flooding when two weeks of heavy rain poured over the state from May 29 to June 12.   A statewide average of 9.03 inches of rain fell in this period, probably the greatest 15 day rain total in the state’s history (normal for the period is 2.45 inches).   Flooding was widespread over the southeastern two-thirds of Iowa with record flooding down the length of the Cedar River and along portions of the Des Moines, Iowa and Mississippi Rivers.   Cedar Rapids was hardest hit with a June 13 flood crest 11 feet higher than the previous record.   Statewide an estimated $10 billion in flood damage occurred.   Overall flooding was not as widespread or as long lasting as in 1993, but damage was more severe.   Localized downpours resulted in more flooding in south central Iowa during July.   However, much of the state saw much drier weather after mid June with drought conditions affecting parts of western and far northern Iowa by August.   Annual precipitation totals varied from 26.86 inches at Spencer to over 57.48 inches at Allerton.   Some portions of northwest Iowa recorded slightly less than normal precipitation for the year while very heavy precipitation was the rule over south central, central and east central Iowa.   Although data are not yet complete for some locations record annual precipitation totals were recorded at a few locations such as:

Location          2008 Total       Old Record and Year             Period of Record
Allerton           57.48 inches                53.72 in 1902              104 years
Mount Ayr      55.40 inches                55.02 in 1993              106 years
Cascade           54.29 inches                51.40 in 1993                66 years
Lorimor           53.16 inches                52.06 in 1993                56 years
Beaconsfield   52.29 inches                51.96 in 1993                52 years

Snowfall was unseasonably heavy in both February and December.   Oskaloosa recorded 41.7 inches of snow in February while Waukon saw 34.9 inches of snow in December.   Based upon statewide averages it was the 3rd snowiest February and 4th snowiest December among 121 years of records.   The calendar year of 2008 ranks 7th snowiest of record statewide, and comes among several other very snowy years recently (2007 ranked 9th, 2000 was 8th and 1997 2nd).

Severe Weather.   The 2008 severe weather season got off to a fairly slow start; however, that was to change abruptly and tragically on May 25.   Iowa’s first F5 tornado since 1976 struck Parkersburg and nearby areas in the early evening of May 25 resulting in eight fatalities and an estimated $100 million in damage.   An F3 storm struck the Little Sioux Scout Camp on June 11 resulting in another four fatalities.   Overall the 12 deaths was Iowa’s highest annual number of tornado-related fatalities since 1968.   The National Weather Service reported a total of 105 tornadoes in the state in 2008, tying with 2001 as the second greatest annual total behind a tally of 120 twisters in 2004.   The average annual number of tornadoes in Iowa during the Doppler radar era (when tornado detection and reporting improved greatly) is 56.   Fortunately, the second half of the year was much quieter with 16 tornadoes, none of which was stronger than F1 intensity.

Outlook.   As we begin 2009, soil moisture levels are generally greater than normal for this time of year except across portions of northeastern Iowa where soils are a little drier than usual.   Central and southeastern sections are the wettest with soil moisture estimated by the Midwestern Regional Climate Center to be similar to what they were at this time last year.   Snowpack water content across the northern one-third of the state is generally similar to what it was entering 2008.   However, the snow pack is nearly gone across southern Iowa while substantial moisture remained frozen on the ground at this time last year.

La Niña conditions (cool in the tropical Pacific) have again become established, although the pattern is not as mature as at this time a year ago.   Historically La Niña slightly favors cooler and wetter than normal weather in Iowa during January and February.   March typically has been a little cooler and frequently drier than usual with La Niña in place.   The historical La Niña pattern favors wetter and slightly cooler than normal weather in April.   Generally the odds increasingly favor drier than normal weather starting in June but with temperatures averaging near seasonal norms.   Overall, La Niña favors a drier year for 2009 and slightly favors cooler weather as well.   Of course La Niña was in place last year at this time with the same general expectations when atypical wetness prevailed through May and June.

Harry Hillaker, State Climatologist
Iowa Dept. of Agriculture & Land Stewardship
Wallace State Office Bldg.; Des Moines, IA 50319
Phone: (515) 281-8981


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Mailing Address: IDALS,  Wallace State Office Building,   502 E. 9th Street,  Des Moines, IA 50319:    PH: 515-281-5321
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