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Recapping Iowa’s 2011 weather

By Staff | Jan 6, 2012

By HARRY HILLAKER/State climatologist

DES MOINES – Preliminary analysis shows that in 2011 Iowa experienced an average temperature of 48.8 degrees, or 0.7 degrees above normal, and had a statewide average of 32 inches of precipitation, or 3.27 inches less than normal,.

The result is that 2011 ranks as the 50th warmest year and 68th driest among 139 years of state weather records.

“The weather is always a hot, or cold, topic in Iowa, and Harry does a great job collecting the information and making it available to Iowans,” said Bill Northey, Iowa Secretary of Agriculture. “There was no shortage of interesting weather events again in 2011 and this is a great list of the highs and lows.”

The top Iowa weather events in 2011 in chronological order are:

  • Blizzard: Jan. 31 to Feb. 2 (mostly on Feb 1). Snow fell statewide with over a foot of snow across southeast and east central Iowa.

Storm totals recorded 18.5 inches at Lowden and a record-tying 18.4 inches at the Quad Cities. Strong wind gusts were also reported, with gust of 66 mph at Clinton.

The simultaneous occurrence of the highest winds with the most intense rate of snowfall resulted in very poor visibility.

The storm produced a statewide average of 7.4 inches of snow.

  • Tornados: April 9. A total of 20 tornadoes were reported on the evening of April 9, mostly across west central and northwest Iowa.

The most damaging of the series was the very first storm which brought EF-3 damage to Mapleton.

  • Hot and Cold May: May 3 and May 10. A nearly statewide freeze occurred May 3 with temperatures as low as 20 degrees at Sibley and Spencer.

Lower May temperatures have been recorded only four times in the past 100 years in Iowa.On the 10th, temperatures soared into the 90s over nearly all of Iowa with Jefferson reaching 100 degrees.

This was the earliest occurrence of triple digit heat in Iowa since April 22, 1980.

  • Wet weather: June. Very wet weather prevailed across southeast Iowa with Keosauqua (16.14 inches) and Bloomfield (14.60 inches) recording the most rain of record at those locations for any calendar month.
  • Western Iowa flooding: May through September. Easily the largest weather event of 2011 was the flooding along the Missouri River.

Record crests were set at gaging points near Mills County (June 30) and Fremont County (June 28).

Major flooding persisted for several months in response to very wet antecedent conditions in the Upper Missouri basin, a large winter snowpack, rapid snow melt following an unusually cold spring and excessive upstream spring rainfall.

Fortunately, no major rain events occurred in the Iowa portion of the watershed during 2011.

  • July heat: July. Preliminary data show Iowa experienced its hottest July since 1955 and hottest calendar month since August 1983.

Actual temperatures peaked at 102 degrees at Keosauqua on July 18 with a peak official heat index of 117 degrees at Spencer (also on the 18th).

  • Derecho: July 11. Widespread very high winds occurred across parts of east central Iowa in the pre-dawn hours of July 11 with winds estimated as high as 130 miles per hour in Benton County.

Later that same day, Iowa’s last tornado of the year touched down in Webster County. Iowa saw a very early start to the tornado season, with outbreaks on March 22 and April 9, but also the earliest end to the season since 1962.

  • Heavy rain storms: July 26 to July 27. Very heavy rain fell across portions of northeast Iowa on the night of July 26 with the heaviest rains falling in the Dubuque area, where the airport saw a record 24-hour total of 10.62 inches of rain and unofficial totals were as high as 14.5 inches.

The rain contributed greatly to a record monthly total of 16.01 inches at the Dubuque Airport (old record 15.46 inches in September 1965 among 158 years of data in the area).

  • Record hot day: Aug. 2. Temperatures soared across southeast Iowa in advance of a cool front with Fairfield recording an actual temperature of 106 degrees.

This was Iowa’s highest official reading since Washta reached 106 on July 19, 2006.

Iowa City saw the highest official heat index that afternoon with a reading of 117 degrees.

  • Drought: July to December. The high mid- and late-summer temperatures were a reflection of very dry conditions that rapidly developed in July.

Southeast Iowa was the first area to turn dry (ironically after seeing record rains in June) with Fairfield recording only 0.17 inch of rain in July.

Dry conditions spread to all but portions of east central and northeast Iowa by September.Relief in the form of several large rain events came to many areas in November and December, but severe drought conditions persist at year’s end over about the northwest one-quarter of the state.

The late year dryness allowed for a very rapid completion of Iowa’s harvest (98 percent of the soybeans harvested by the end of October).

However, at the same time, the state’s pastures were in their worst condition in eight years.

  • Early freeze: Sept. 15. Nearly half of Iowa saw a freeze on the morning of Sept. 15 with Mason City reporting a low of 26 degrees. This was Iowa’s lowest temperature for so early in the fall since Sibley reported 23 degrees on Sept. 11, 1955.

At Jefferson and Cedar Rapids this tied for the earliest freeze on record.

  • Warm December. Dec. 11 to 31: The last three weeks of the year were very mild with temperatures averaging 12.6 degrees above normal, while an average of only 0.3 inches of snow fell across Iowa. This was a huge contrast from the previous four Decembers which were all unusually cold and snowy.

However, more seasonal weather occurring during the first 10 days of the month will keep the month out of the top ten for warmth and lack of snow (in fact, December 2006 was warmer and had less snow).

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