THE FOLLOWING TABLES GIVE A MONTH BY MONTH BREAKDOWN OF WEATHER IN 2013 AT THE SIOUX CITY AIRPORT...
MONTH AVERAGE DEPARTURE EXTREMES MONTHLY MAX MIN MONTHLY FROM NORM HIGH LOW RECORDS JANUARY 30.7 10.5 20.6 PLUS 0.2 55 -5 FEBRUARY 35.8 15.3 25.5 PLUS 0.4 52 -7 MARCH 40.5 21.5 31.0 MINUS 5.5 67 4 APRIL 55.7 31.7 43.7 MINUS 5.9 86 16 6TH COLDEST 3RD SNOWIEST MAY 70.6 48.3 59.4 MINUS 1.4 106 29 4TH SNOWIEST JUNE 79.9 59.7 69.8 MINUS 0.5 94 45 JULY 85.9 61.0 73.5 MINUS 0.8 94 44 6TH DRIEST AUGUST 83.4 62.9 73.1 PLUS 1.0 92 51 SEPTEMBER 81.2 55.6 68.4 PLUS 5.0 94 34 11TH WARMEST OCTOBER 62.6 37.6 50.1 MINUS 0.6 88 24 8TH WETTEST NOVEMBER 47.5 22.0 34.8 MINUS 1.0 62 4 DECEMBER 28.8 7.1 18.0 MINUS 4.6 62 -11 10TH DRIEST 2013 58.6 36.1 47.3 MINUS 1.3 106 -11
DEPARTURE DEPARTURE MAX WIND GUST MONTH FROM NORM SNOWFALL FROM NORM DIRECTION/MPH/DATE JANUARY 0.19 MINUS 0.43 1.4 MINUS 5.3 N 43 ON 19TH FEBRUARY 1.01 PLUS 0.34 9.4 PLUS 2.8 NW 47 ON 18TH* MARCH 2.00 0 11.7 PLUS 5.2 NW 48 ON 5TH APRIL 4.85 PLUS 1.90 11.2 PLUS 9.4 NW 49 ON 24TH MAY 5.28 PLUS 1.54 1.4 PLUS 1.4 NW 45 ON 16TH JUNE 3.13 MINUS 0.76 SW 47 ON 22ND JULY 0.60 MINUS 2.84 N 44 ON 19TH AUGUST 3.07 MINUS 0.16 W 44 ON 21ST SEPTEMBER 1.44 MINUS 1.52 NW 44 ON 19TH OCTOBER 3.89 PLUS 1.76 T MINUS 1.0 S 44 ON 11TH NOVEMBER 1.09 MINUS 0.22 0.9 MINUS 3.5 NW 47 ON 1ST DECEMBER 0.18 MINUS 0.62 2.3 MINUS 5.5 NW 61 ON 28TH 2013 26.73 MINUS 1.01 38.3 PLUS 3.5 NW 61 DEC 28TH * LAST OF SEVERAL OCCURRENCES FOR MONTH
2013 did not deviate too far from a normal year when looking at the entire year...a shade cooler and drier than the long term average. The mean temperature for the year was 1.3 degrees below normal...while precipitation ended the year 1.01 inches on the shy side. Snowfall for 2013 at 38.3 inches did manage to sneak a bit above normal /3.5 inches/. For the most part...these yearly numbers did fall close to the middle of the long term climatic record. However...parts of the year proved to be extreme on both sides...which resulted in an annual average close to normal. There were 13 days with below zero lows...and 24 days with highs of 90 degrees or higher.
The winter of 2012-2013 closed out fairly close to normal. January was a dry month...and a stretch of seasonable weather to start the month gradually melted the 4 inches of snow cover which greeted the New Year. There was even a pure light rainfall event on the 10th. Warmest readings appeared mid-month...when the warmest high of 55 degrees occurred. As the warmth broke...the most significant precipitation of the month occurred on the 20th when around an inch of snow fell. A few days later...the temperatures returned back to well above normal readings...until the final day of the month. Cool and windy conditions on the 31st took wind chills to 20 below to 30 below zero.
The frigid conditions were very brief...as the first half of February featured 13 consecutive above normal days. There was even a thunderstorm observed on the 10th. The warmth would be balanced by a stretch of 10 consecutive below normal days to end the month...resulting in near normal temperatures for the month. In the midst of the cold stretch...a winter storm brought 8.9 inches snowfall on the 21st and 22nd...nudging the monthly snow total above normal...and blanketing the area with the greatest snow depth of the winter at 9 inches. The precipitation of 0.62 inches on the 21st was a record for the date.
For the winter season of 2012-2013 /December through February/ was somewhat wetter than normal at 2.87 inches...and also somewhat warmer than normal at 23.9 degrees.
March continued trends from late February with only 8 days of the month ending up above normal. The mean temperature for the month was 5.5 degrees below normal at 31.0 degrees...a sharp contrast from 2012...when the warmest march occurred with a mean temperature of 53.2 degrees...a 22.2 degree year to year change! Despite normal precipitation in March...the cold temperatures meant a greater amount of snowfall...with 11.7 inches during this snowiest month of the year. A majority of this snow occurred with a winter storm on the 9th and 10th...when 9.8 inches fell. The precipitation for the 9th was a record for the date at 0.71 inches...and a snowfall on the 10th of 6.6 inches was a record for the date. A brief warm-up managed to melt all 9 inches of snow in just 4 days by the 15th. However...cold air came back to dominate most of the rest of the month with the next 13 days below normal accompanied by periodic light snowfall. A thunderstorm was observed on the 30th with around a third of an inch of rainfall.
Chilly early spring conditions continued in April...with a few brief warm periods permeating a longer term cold trend. Most of the warmer weather was very early and very late in the month...with the first 70 degree reading of the year on the 6th...and the first 80 degree reading on the 28th. Sandwiched in the middle was a chilly and occasionally snowy period. The most significant weather event of the month was a significant winter storm which brought first heavy rainfall to the area on the 9th...then a mix of snow...sleet and freezing rain for the following couple of days. Precipitation of 2.33 inches on the 9th was not only a record for the date...but the second greatest precipitation for any April day on record. This precipitation...along with a pair of additional spring storms on the 17th/18th /record 4.7 inches/ and the 22nd /record 1.5 inches/ helped push April 2013 to be the third snowiest April on record /11.2 inches/...and the 10th wettest April /4.85 inches/. Following the snowfall...two record lows were established with 22 degrees on the 20th...and 25 degrees on the 25th.
May proved to be one of the most extreme months of the year. The month started with a rare May snowfall of 1.4 inches. This was the first measurable snowfall in May since 1946. While the first 12 days of the month were below normal with the final freeze of the year on the 12th...the next two days saw the first 90 degree reading on the 13th...and the warmest day on record for may on the 14th with 106 degrees. This was the warmest reading of the year for Sioux City. After the wild changes early in the month...conditions settled to a more normal regime. Rainfall for the month featured periodic modest amounts...with the next greatest amount after the rain/snow on the 1st measured at 1.02 inches on the 27th.
Meteorological spring /March through May/ ended up 12th coldest and 10th wettest. It was also the coldest spring season since 1996.
June overall was a fairly normal month...slightly below normal to start the month and slightly above normal to finish. The warmest low temperature of the year occurred on the 21st at 79 degrees. Despite numerous thunderstorms during the month...precipitation ended up a bit below normal. Thunderstorm outflow early on the morning of the 22nd produced wind gusts to 47 mph.
A change to a more pronounced dry period started in July...and the month was the 6th driest July on record. Only a single event produced more than a quarter inch or rainfall...with 0.40 inches on the 25th. Severe weather also remained sparse...with thunderstorms on the 7th resulting in the strongest measured wind of the month at 44 mph but only a trace of rainfall. Tree damage was reported in the Leeds area during the late evening. Temperatures were fairly close to normal much of the month...but a sharply colder period toward the end of the month produced a pair of record lows on the 27th /47/ and 28th /44/...along with a record cold maximum temperature of 67 degrees on the 29th.
August 2013 was the first month featuring above normal temperatures since February. While the first 19 days of the month were 4 degrees below normal...those waiting for the true appearance of summer would only have to wait until some kids returned to school. The final week of August was the 4th warmest on record...averaging a high of 91.1 degrees and low of 70.7 degrees. A record high minimum of 76 degrees was recorded on the 25th. A nighttime thunderstorm early on the 22st produced 1.39 inches of rainfall along with wind gusts to 44 mph.
Summer 2013 /June through August/ was the 16th driest with 6.80 inches precipitation. Temperatures were fairly close to normal with a mean of 72.1 degrees. Even with the lack of precipitation...the modest temperatures overall kept drought conditions from worsening during the summer.
The month of September brought the first...and only...solidly above normal temperatures of the year. Only 6 days of the month were below normal...and of those...only two were more than 5 degrees below normal. The month ended as the 11th warmest September on record. Less than half of normal precipitation fell for the month...and most of that was in the first week of the month.
Certainly the most significant weather event during 2013 occurred during the month of October. A very late season tornado outbreak occurred on October 4 across Siouxland...with over a dozen tornadoes reported...and producing a pair of long track ef4 tornadoes. One of these struck the community of Wayne Nebraska...and a second touched down near climbing hill...travelling northeast for 25 miles before lifting west of Washta. The maximum intensity of this tornado occurred while it was just southeast of Pierson.
Otherwise...the warm weather early in the month was balanced by some late month cooling for a near normal temperature. The first freeze of the fall occurred on the 13th...although some patchy frost was noted around the area with lows just above freezing on September 21. Heavy rainfall of 2.31 inches on the 14th /4th all-time wettest October day/ helped push the month to being the 8th wettest on record. The first snowfall of the year occurred on the 23rd...with a trace.
Most of the precipitation for November was recorded on the 5th...when 0.92 inches and 0.5 inches snow fell at Sioux Gateway Airport. Otherwise...the month was again drier and less snowy than normal. A warm mid-month period was bracketed by much cooler than normal temperatures on each side. The warmest reading of the month occurred on the 19th at 62 degrees...and this was followed a week later with the coolest readings of the month at 4 degrees on the 27th. The very chilly air building southward just before thanksgiving made for the first day failing to reach freezing on the 22nd. The strong high pressure area bringing the cold air resulted in a record high pressure for the month of November on the 23rd at 30.96 inches.
December 2013...while ranking outside the top 10 coldest...might have finished as such if not for a run of mild temperatures right after Christmas...resulting in a pair of record high temperatures late in the month on the 27th and 28th /59 and 62 respectively/. The month featured some drastic changes in temperatures with periodic arctic air intrusions not seen for several years this early in the season. The first below zero reading was reported on the 6th...which was about a week earlier than the average date over the period of record. The dry conditions of later November persisted through December...ending up 10th driest at 0.18 inches. Only 2.3 inches of snow fell in December in Sioux City. And overall...it was a dry and fairly snowless start to the 2013-2014 winter...with snowfall 9 inches below normal in November and December.