By Joe Sheehan
Climatic Focal Point
National Weather Service, Sioux Falls

The year 2010 will be most remembered for the excessive rainfall during the summer, the wettest on record. The total rainfall for the three month period of June, July and August was 22.64 inches, easily surpassing the previous wettest summer of 1993 when 17.39 inches fell. The 22.64 inches of rain is more than double the average rainfall of 9.43 inches and only 2.05 inches shy of what is normally expected for the entire year! The record rainfall during the summer months helped boost the total precipitation for the year to 38.26 inches, the wettest on record. The previous wettest year was 36.11 inches in 1993. The thunderstorms began in earnest on June 10th and continued into September. The storms brought several rounds of flash flooding and strong damaging winds. The highest wind gust for the year of 63 mph occurred during a thunderstorm shortly after 6 pm CDT on June 26 that brought a quick 1.72 inches of rainfall at the airport. The greatest 24 hour rainfall occurred July 21 and July 22 when nearly three inches fell, /2.98 inches/. The final heavy rain event occurred in the third week of September when 0.73 inches fell on the 22nd and 1.42 inches on the 23rd. For storm weary farmers anxious to harvest, a dry period began on September 24th and continued through October 24th with only 0.09 inches of rain during this month long period.

A total of 7.83 inches of rain fell during the month of June making it the 4th wettest on record. The month of July was 2nd wettest on record with 8.55 inches, about a half inch shy of the record wettest of 9.11 inches set in 1900. A total of 6.26 inches fell in August, making it the 9th wettest.

Temperatures during June and July were close to normal, with August 3.5 degrees above normal. The hottest day of the year occurred on July 27th with a reading of 94 degrees.

The year started with deep snow cover left over from the Christmas 2009 snowstorm. The greatest snow depth of the year was measured on January 7th and 8th at 20 inches. The coldest temperature of the year was 30 degrees below zero on the 2nd of January. It was the first 30 below zero reading recorded since New Years Day in 1974 when the mercury plunged to 32 below zero. Snowfall for the months of January and February was above normal with 8.4 and 16.9 inches respectively. The 16.9 inches during February is the tenth snowiest on record. 19 inches of snow was measured on the ground on February 14th through the 16th. Much of the snow melted during a stretch beginning March 6th through the 18th when continuous cloud cover and on and off light rain and drizzle fell. Nighttime minimum temperatures during the period were near or above freezing while maximum temperatures in the middle 30s at the start of the period warmed to 58 degrees on the 18th. A total of 0.87 inches of precipitation fell during this time including a half inch of snow on the 11th. The precipitation and snowmelt combined to produce significant flooding on the Big Sioux River in Sioux Falls. Thankfully only a trace of precipitation fell from March 15th to the end of the month.

The months of January and February were below normal by 3.5 and 6.2 degrees respectively. Above normal temperatures occurred during March, /plus 4.9 degrees/, and April, /plus 6.5 degrees/.

The months of October and November were quiet with below normal precipitation and above normal temperatures. One notable event occurred on October 25th and 26th when low pressure deepened rapidly bringing strong westerly winds and nearly an inch of rain, /0.89 Inches/. Peak wind gusts of 52 mph were measured on the 26th and 58 mph on the 27th. This is the super storm that set a record low barometric pressure in Minnesota on the 26th.

The weather pattern changed during December with above normal snowfall and below normal temperatures. The biggest snow of the year occurred on the 11th with 7.6 inches. This storm was accompanied by northerly winds gusting to 53 mph, creating blizzard conditions. The 17.9 inches snowfall for the month is the 6th snowiest December on record.

The average temperature for the year of 48.1 degrees was three degrees above normal. The average maximum temperature for the year was 58.1 degrees, about a degree above normal, while the average minimum temperature of 38.1 degrees was around five degrees above normal. The year had a total of 8 days with temperatures of 90 degrees of more. A maximum temperature of 32 degrees or colder occurred on a total of 60 days. The minimum temperature fell to 32 degrees or colder on 105 days and zero degrees or colder on a total of 24 days.



                AVERAGE             DEPARTURE  EXTREMES   MONTHLY

JANUARY       18.9   2.2     10.5   MINUS 3.5   38  30B
FEBRUARY      23.4   5.9     14.6   MINUS 6.2   35  16B
MARCH         45.9  29.0     37.5    PLUS 4.9   80   5
APRIL         64.4  39.9     52.2    PLUS 6.5   79  26
MAY           68.6  44.9     56.7   MINUS 1.1   91  28
JUNE          77.5  57.6     67.6    PLUS 0.1   89  48  4TH WETTEST
JULY          83.6  63.4     73.5    PLUS 0.5   94  55  2ND WETTEST
AUGUST        84.1  64.5     74.3    PLUS 3.5   92  51  9TH WETTEST
SEPTEMBER     70.6  49.3     59.9   MINUS 1.0   87  40
OCTOBER       64.3  38.3     51.3    PLUS 3.3   84  24
NOVEMBER      43.6  24.2     33.9    PLUS 2.6   71   2
DECEMBER      25.0   7.7     16.4   MINUS 1.9   48   7B

 2010         58.1  38.1     48.1    PLUS 3.0   94  30B
NORMAL YEAR   57.2  33.0     45.1  


                 DEPARTURE             DEPARTURE   MAX WIND GUSTS 

JANUARY   1.25   PLUS  .74      8.4    PLUS  1.0    NW 53 ON 25TH
FEBRUARY  1.29   PLUS  .78     16.9    PLUS 11.0    NW 36 ON 14TH
MARCH     1.02  MINUS  .79      0.5   MINUS  7.6     S 38 ON 22ND
APRIL     2.65           0       0    MINUS  3.5     S 48 ON 13TH
MAY       2.03  MINUS 1.36       0                   S 51 ON 24TH
JUNE      7.83   PLUS 4.34       0                  NW 63 ON 26TH
JULY      8.55   PLUS 5.62       0                  NW 43 ON 27TH
AUGUST    6.26   PLUS 3.25       0                   S 61 ON 19TH
SEPTEMBER 4.46   PLUS 1.88       0                   N 56 ON 15TH
OCTOBER    .91  MINUS 1.02       T    MINUS  1.1     W 58 ON 27TH
NOVEMBER   .47  MINUS  .89      1.1   MINUS  6.5    NW 51 ON  3RD
DECEMBER  1.54   PLUS 1.02     17.9    PLUS 10.9     N 53 ON 11TH

 2010    38.26  PLUS 13.57     44.8    PLUS  4.2    NW 63 JUNE 26TH is the U.S. government's official web portal to all federal, state and local government web resources and services.