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

The big weather story of 2010 in Sioux City was the excessive rainfall during the summer months of June...July and August which totaled 20.13 inches...making it the wettest summer on record. The previous wettest summer occurred during the great flood year of 1993...when 17.37 inches fell. The 20.13 inches of rain is more than double the normal amount of 9.81 inches that usually falls during the three month period. Almost half of this rainfall occurred during July when a whopping 9.23 inches fell...the second wettest July on record. Much of the rain fell during the second half of the month with 1.61 inches on the 19th... 2.75 inches on the 22nd... 2.11 inches on the 29th and 0.82 inches on the 30th. The greatest 24 hour rainfall of the year /2.88 inches/...fell on the night of July 21st and 22nd...with 1.74 inches falling between 2 and 3 am CDT. The wettest July occurred in 1972 with 10.33 inches.

The total precipitation for the year was 32.05 inches...a little more than six inches above the normal of 25.99 inches. This continues the trend of above normal precipitation in recent years with 32.82 inches during 2009…31.64 inches in 2008 and 39.58 inches in 2007.

The year started out cold and with plenty of snow left over from the Christmas 2009 storm. The coldest temperature of the year occurred on January 2nd and again on the 4th at 22 degrees below zero. A total of 6.6 inches of snow fell on the 6th and 7th...with a total snow depth of 28 inches measured on the morning of the 7th through the 10th. This is the greatest snow depth for the year...and equals the all time greatest depth of snow for the city measured on March 13 1962. Precipitation for January and February were above normal and when combined with December 2009...produced the fourth wettest winter on record with 4.68 inches of precipitation.

A pattern change in the weather brought above normal temperatures during March and April. Beginning on March 6th there was a string of 12 consecutive days with the temperature remaining above freezing. Nighttime lows varied from 33 to 36 degrees while daytime highs were well into the 30s and 40s. Much cloudiness and occasional rain...drizzle and fog accompanied this time frame with a total of 1.26 inches of rain. Any remaining snow on the ground melted and combined with upstream melting brought river flooding to the area. The Missouri river stage went from a level around 11 feet on the 8th to 23.6 feet on the 19th. Fortunately from March 14th to the end of the month only 0.12 inches of additional precipitation fell. The month of April had about half the normal rainfall while the average temperature of 55.4 degrees is the 7th warmest on record.

The months of May...June and July had temperatures close to normal. The hottest day of the year occurred on May 24th when the mercury rose to 95 degrees. Only 1.41 inches of rain fell during May...the ninth driest on record.

The highest wind gust of the year occurred during the early evening of August 8th when a thunderstorm produced a wind gust to 66 mph at 722 pm CDT along with 1.50 inches of rainfall.

The autumn months of September through November were near to above normal in temperature. A record high of 93 degrees was reached on October 8th...the hottest temperature recorded so late in the season. The month of September had 2.99 inches of rain...about a half inch above normal while October and November were both around an inch below normal. A notable event occurred on October 25th and 26th when low pressure deepened rapidly across the area bringing strong westerly winds and nearly an inch of rain.../0.93 inches/. Westerly winds gusted to 51 mph on the 26th and 27th. This is the super storm that set a record low barometric pressure in Minnesota on the 26th.

December was around 2 degrees below normal while precipitation was above normal. Blizzard conditions existed on the 11th with 4.4 inches of snow and northwest winds gusting to 55 mph.

The average temperature for the year was 51 degrees...or 2.7 degrees above normal. The average maximum for the year was 61.9 degrees...which is 2.4 degrees above normal and the average minimum was 40.1 degrees... 3.1 degrees above normal. The year had a total of 22 days with temperatures of 90 degrees or more. A maximum temperature of 32 degrees or colder occurred on 51 days. The minimum temperature fell to 32 degrees or colder on 105 days and zero degrees or colder on 17 days.



                AVERAGE               DEPARTURE  EXTREMES   MONTHLY

JANUARY       21.1   5.8     13.5     MINUS 5.1   38  22B 10TH WETTEST
FEBRUARY      26.0  10.0     18.0     MINUS 7.1   36   7B
MARCH         48.2  30.2     39.2      PLUS 2.7   79   9
APRIL         68.9  41.8     55.4      PLUS 5.9   86  27  7TH WARMEST
MAY           73.9  47.4     60.7     MINUS 0.5   95  30  9TH DRIEST
JUNE          83.3  60.3     71.8      PLUS 1.3   94  47
JULY          85.7  64.5     75.1      PLUS 0.5   94  56  2ND WETTEST
AUGUST        86.4  65.4     75.9      PLUS 3.8   94  53 
SEPTEMBER     76.8  51.1     64.0      PLUS 0.9   93  42 
OCTOBER       69.7  38.4     54.1      PLUS 3.3   93  25 
NOVEMBER      48.3  24.8     36.5      PLUS 1.7   78   6 
DECEMBER      29.3  10.9     20.1     MINUS 2.2   52   4B

 2010         61.9  40.1     51.0

NORMAL YEAR   59.5  37.0     48.3


                DEPARTURE             DEPARTURE    MAX WIND GUSTS
JANUARY   1.43   PLUS  .84     13.6    PLUS 7.3     NW 55 ON 25TH
FEBRUARY   .87   PLUS  .25      9.9    PLUS 4.4     NW 44 ON 14TH
MARCH     1.38  MINUS  .62      0.5   MINUS 5.3      S 36 ON 30TH
APRIL     1.49  MINUS 1.26       0    MINUS 1.9      S 49 ON 28TH
MAY       1.41  MINUS 2.34       0                   S 49 ON 24TH
JUNE      6.40   PLUS 2.79       0                   W 52 ON 11TH
JULY      9.23   PLUS 5.93       0                  NW 40 ON 23RD
AUGUST    4.50   PLUS 1.60       0                  NW 66 ON  8TH
SEPTEMBER 2.99   PLUS  .57       0                  NW 44 ON 25TH
OCTOBER    .95  MINUS 1.04       0    MINUS  .8      W 51 ON 27TH
NOVEMBER   .45  MINUS  .95      0.2   MINUS 4.6     NW 47 ON 30TH
DECEMBER   .95   PLUS  .29     10.2    PLUS 3.9     NW 55 ON 11TH

 2010    32.05   PLUS 6.06     34.4    PLUS 3.0     NW 66 AUG 8TH is the U.S. government's official web portal to all federal, state and local government web resources and services.