SIOUX FALLS AREA
CLIMATIC SUMMARY
2004

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

 

...MORE PRECIPITATION EXTREMES THAN TEMPERATURE EXTREMES IN 2004...

2004 was overall a wet and mild year in Sioux Falls. Several major rainfall events made for an above normal precipitation year with a total of 30.92 inches at the airport...compared to a normal of 24.69 inches. Up to 35 inches precipitation was reported in southern Sioux Falls. Temperatures averaged 46.6 degrees in 2004...or 1.5 degrees above normal.

Above normal snowfall occurred in the 2003-04 winter season with a total of 56.6 inches. 41.5 inches of this snowfall was recorded from December 2003 through February 2004. Normal snowfall for the entire season is 40.6 inches...and for December through February is 20.3 inches. A lot of the snow occurred within a 12-day period from January 25th to February 5th with a total of 25.9 inches at the airport...and the average snow depth built up to as high as 22 inches by February 6th. The coldest temperature of both the year and the season was recorded within this period with a low of -18 on January 27th. The first half of February remained very cold with notable lows of -14 on the 3rd and -12 on the 15th. However...the last half of February was much warmer and all of the snow on the ground had melted by the end of the month. This warm temperature trend continued into March and April...with March averaging 5.9 degrees above normal and April 3.3 degrees above normal. One last snow event did occur from March 15-16th with 5.1 inches measured at the airport, and then only a trace of snowfall occurred the remainder of the season.

The severe weather season started April 18th with some hail up to golf-ball size reported in Sioux Falls between 515-525 pm CDT. However...overall it was a rather dry and pleasant springtime period from April through the first half of May with 1.94 inches rainfall recorded at the airport. Then the pattern reverted to wet...really wet...from late May to mid June...with two major rain events and resultant flash flooding in Sioux Falls on May 29th and June 16th. Both events caused flooding of many homes and roads in Sioux Falls. At the airport 4.22 inches was recorded on May 29th and 3.58 inches on June 16th. There were other reports up to 6 inches around Sioux Falls between 6 pm and midnight on May 29th...and up to 7.50 inches in southwest Sioux Falls between 4 am and 8 am on June 16th. The 4.35 inches of rainfall that occurred at the airport within a 24 hour period from May 29th-30th was the heaviest 24 hour precipitation event in the official records for the month of May...and the third heaviest 24 hour event for any month. With the event on June 16th...Sioux Falls ended up with the wettest 31 day or monthly period on record...with a total of 12.74 inches rainfall.

There was also some hail up to 1 inch in diameter in the Sioux Falls area on the following dates...May 26th at 7 pm...May 28th around 7 pm...with the storms on May 29th...and then on July 31st at 730 pm. The next big severe weather event in the area occurred the late morning of August 3rd...mainly north of interstate 90 where derecho thunderstorm winds gusted up to 90 mph. These widespread strong winds caused damage near Hartford around 11 am moving through Garretson around noon. Heavy rains also caused some flooding of roads and low areas north of interstate 90...and 1.89 inches of rain fell at Sioux Falls airport. The last reported severe weather of the season occurred in the early evening of September 13th with hail up to an inch in diameter in Sioux Falls.

A big weather story of the summer after the late spring floods was the unusually cool temperatures. It was the third coolest summer since climatic records started in 1893...with an average temperature of 66.9 degrees for the summer months of June...July...and August. All three of the summer months were below normal...with August the 3rd coolest August on record. The last time all three summer months were below normal was in 1992. Record daily lows occurred on August 14th with 43 degrees...on August 19th with 39 degrees...and on August 21st with 40 degrees. Sioux Falls had only 6 days of 90 degrees or more in 2004...compared to a normal of 20 days. The temperature failed to reach 90 degrees in August for the first time since 1985.

Then there was the typical big seasonal turnaround...with the rest of the year well above normal in temperatures overall. The average temperature in September was 0.3 degrees warmer than in August. This is an unusual event...as there were only two other years on record...1908 and 1897...in which September was warmer than August. Needed rain occurred in September with 5.12 inches rainfall...as the rest of the year was very dry. There was a record daily high of 73 degrees on November 6th. November averaged 6.1 degrees above normal...and December was 7.4 degrees above normal. A record high of 59 on December 30th was also the warmest temperature ever recorded in the 25 day period from December 19th through January 12th.

Of course the total lack of snow cover had a lot to do with the mild temperatures. The first trace of any snowfall this season occurred on November 27th...the second latest trace on record. The first measurable snow of the season of 0.2 inch on December 20th was the latest on record before seeing the first measurable snow...which is defined as at least a tenth of an inch of snowfall. This broke the previous record for latest measurable snow and also trace on December 7th 1963. It was also the longest period on record between measurable snowfalls...279 days from March 17th to December 20th. By the end of the year...there was still only 0.5 inch of snowfall for the season...the least on record through December 31st. Most of the previous was based on snowfall records since 1946...as before that there were minor gaps in the daily snowfall data. The average first date of measurable snow in Sioux Falls is November 2nd.

THE FOLLOWING TABLES GIVE A MONTH BY MONTH BREAKDOWN OF WEATHER IN 2004 AT THE SIOUX FALLS AIRPORT...

TEMPERATURES

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

JANUARY 25.2 4.5 14.9 PLUS 0.9 54 18B
FEBRUARY 28.1 12.4 20.3 MINUS 0.5 47 14B
MARCH 49.2 27.7 38.5 PLUS 5.9 75 8
APRIL 63.5 34.5 49.0 PLUS 3.3 89 21
MAY 69.4 46.1 57.8 ZERO 90 28 5TH WETTEST
JUNE 75.9 53.6 64.8 MINUS 2.7 91 41
JULY 80.9 60.0 70.5 MINUS 2.5 91 48
AUGUST 77.2 53.8 65.5 MINUS 5.3 88 39 3RD COOLEST
SEPTEMBER 76.6 54.9 65.8 PLUS 4.9 89 34
OCTOBER 60.8 38.8 49.8 PLUS 1.8 75 23
NOVEMBER 48.2 26.7 37.4 PLUS 6.1 73 13
DECEMBER 35.3 16.0 25.7 PLUS 7.4 59 7B

2004 57.5 35.8 46.6 PLUS 1.5 91 18B

NORMAL YEAR 57.2 33.0 45.1

PRECIPITATION (INCHES) AND WINDS

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

JANUARY .52 PLUS .01 12.3 PLUS 4.9 NW 48 ON 14TH
FEBRUARY 1.11 PLUS .60 15.8 PLUS 9.9 NW 39 ON 20TH
MARCH 2.03 PLUS .22 7.4 MINUS 0.7 NW 47 ON 8TH
APRIL 1.28 MINUS 1.37 T MINUS 3.5 NW 54 ON 18TH
MAY 8.10 PLUS 4.71 0 S 48 ON 11TH
JUNE 6.00 PLUS 2.51 0 N 38 ON 16TH
JULY 1.40 MINUS 1.53 0 N 44 ON 3RD
AUGUST 3.58 PLUS .57 0 N 56 ON 3RD
SEPTEMBER 5.12 PLUS 2.54 0 W 43 ON 13TH
OCTOBER .86 MINUS 1.07 0 MINUS 1.1 NW 47 ON 30TH
NOVEMBER .81 MINUS .55 T MINUS 7.6 N 35 ON 10TH
DECEMBER .11 MINUS .41 0.5 MINUS 6.5 NW 49 ON 12TH

2004 30.92 PLUS 6.23 36.0 MINUS 4.6 N 56 AUG 3RD


RICHARD S. RYRHOLM/ CLIMATIC FOCAL POINT

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