SIOUX CITY AREA
CLIMATIC SUMMARY
2007

By Richard Ryrholm
Climatic Focal Point
National Weather Service, Sioux Falls

...WET AND MILD YEAR AT SIOUX CITY IN 2007...

Temperatures averaged 49.1 degrees for 2007, or 0.8 degree above the normal of 48.3 degrees. This was the 10th straight year of above normal temperatures in the Siouxland. The last year below normal was in 1997 with an average of 47.5 degrees. Precipitation was much above normal in 2007, totaling 39.58 inches at the Sioux Gateway Airport, a whopping 13.59 inches above average, for the third wettest year on record.  The wettest year was 56.37 inches, way back in 1881, and the second wettest was 41.10 inches in 1903.  Snowfall totaled 50.6 inches for the 2006-07 snow season, with all but 4.1 inches of this occurring during a 1 1/2 month long period from January 14th to March 2nd.

The following is a chronological account of the weather events of 2007 in Siouxland...

January 8th… The strongest wind of the year occurred at 851 PM at the airport, with a 54 mph gust from the northwest. 50 to 60 mph gusts blew down some 6 to 7 inch diameter tree branches in Sioux City.

January 14-15th… The snow season finally began in earnest with 7.3 inches snowfall.

January 15-16th… Wind chills in the 20s below zero on the 15th were followed by the coldest temperature of the year of  -19 degrees the morning of the 16th.

January 20-21st… 6.2 inches snow fell within a 24 hour period.

February was the snowiest and coldest month of the winter season. Snowfall totaled 20.0 inches for the 5th snowiest February on record, and the temperature averaged 8.1 degrees below normal. 5.7 inches snowfall was recorded the 12-13th, but the heaviest and wettest snow event within a 24 hour period, for the month and the year, was 10.4 inches on the 24-25th.

March came in like a lion, with a blizzard from the 1st to the 2nd bringing a two day total snowfall of 11.1 inches. Strong northwest winds gusting up to 48 mph caused widespread zero visibilities and nearly impossible travel conditions. However, after the first week, it was quite springlike the rest of March and the month averaged 6.2 degrees above normal for the 6th warmest March on record. On the 31st, 2.25 inches of rain pushed the monthly total precipitation to 4.19 inches for the 4th wettest March on record.

April and May were also above normal in precipitation. Heavy precipitation events included 3.14 inches on April 24-25th, and 1.68 inches on May 29th. Hail occurred in the area the evening of May 5th, with golf ball size reported 3 miles east of Sioux City.

June and July were on the dry side, but there was timely rainfall in the middle of each month, with 1.78 inches June 13-14th and 2.15 inches July 18th. Locally very heavy rain caused street flooding in Sioux City the late afternoon of June 16th, but only a trace of rain occurred at the airport where the official gauge is located. However, there were 25 consecutive dry days with a total precipitation of only 0.02 inch from June 23rd through July 17th, for the 2nd driest growing season period on record. The driest such period on record was 0.01 inch in 27 days from July 21st to August 16th 1936. The hottest temperature of 2007 was 98 degrees both July 8th and 17th.

August was the wettest month of a wet year in the Sioux City area, with 9.07 inches for the wettest August on record. The heaviest rain event of the month, and the year, was 4.09 inches within 24 hours the 22-23rd.

September 6th… Another urban flash flood event due to locally heavy rain affected Sioux City in the early evening, but only 0.59 inch was recorded at the airport.

September and October continued the above normal precipitation, with 1.34 inches registered October 7-8th, and 1.90 inches October 14-15th.

November was very dry with a 0.03 inch total for the 3rd driest November on record.

December was back to above normal precipitation, and was also the first below normal temperature month since April. The main event was 0.99 inch precipitation on the 1st with freezing rain bringing around a 1/2 inch of ice accumulation to the area.

THE FOLLOWING TABLES GIVE A MONTH BY MONTH BREAKDOWN OF WEATHER IN 2007 AT THE SIOUX CITY AIRPORT...

TEMPERATURES

                 AVERAGE             DEPARTURE  EXTREMES    MONTHLY
MONTH MAX MIN MONTHLY FROM NORM HIGH LOW RECORDS

JANUARY 29.3 9.3 19.3 PLUS 0.7 50 19B 8TH SNOWIEST
FEBRUARY 24.8 9.1 17.0 MINUS 8.1 47 16B 5TH SNOWIEST
MARCH 53.4 31.9 42.7 PLUS 6.2 84 1 4TH WETTEST
APRIL 60.6 35.6 48.1 MINUS 1.4 93 14
MAY 77.7 53.7 65.7 PLUS 4.5 93 35
JUNE 83.5 60.3 71.9 PLUS 1.4 93 47
JULY 88.6 64.3 76.5 PLUS 1.9 98 50
AUGUST 83.9 65.1 74.5 PLUS 2.4 92 52 1ST WETTEST
SEPTEMBER 77.0 50.6 63.8 PLUS 0.7 91 32
OCTOBER 66.1 42.9 54.5 PLUS 3.7 88 25
NOVEMBER 49.9 23.8 36.9 PLUS 2.1 74 8 3RD DRIEST
DECEMBER 27.0 10.5 18.7 MINUS 3.6 40 4B

2007 60.2 38.1 49.1 PLUS 0.8 98 19B 3RD WETTEST

NORMAL YEAR 59.5 37.0 48.3

PRECIPITATION AND WINDS

                   DEPARTURE             DEPARTURE    MAX WIND GUSTS...
MONTH FROM NORM SNOWFALL FROM NORM DIRECTION/MPH/DATE

JANUARY .87 PLUS .28 15.6 PLUS 9.3 NW 54 ON 8TH
FEBRUARY 1.90 PLUS 1.28 20.0 PLUS 14.5 N 48 ON 16TH
MARCH 4.19 PLUS 2.19 12.3 PLUS 6.5 NW 48 ON 1ST
APRIL 4.64 PLUS 1.89 0.1 MINUS 1.8 NW 46 ON 3RD
MAY 4.74 PLUS .98 0 SE 49 ON 6TH
JUNE 2.70 MINUS .91 0 S 48 ON 6TH
JULY 2.19 MINUS 1.11 0 NW 41 ON 10TH
AUGUST 9.07 PLUS 6.17 0 S 48 ON 20TH
SEPTEMBER 3.67 PLUS 1.25 0 SW 44 ON 30TH
OCTOBER 3.88 PLUS 1.89 0 MINUS 0.8 S 51 ON 2ND
NOVEMBER .03 MINUS 1.37 0 MINUS 4.8 NW 52 ON 14TH
DECEMBER 1.70 PLUS 1.04 12.2 PLUS 5.9 NW 45 ON 22ND

2007 39.58 PLUS 13.59 60.2 MINUS 28.8 NW 54 JAN 8TH

RICHARD S. RYRHOLM..CLIMATIC FOCAL POINT

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