SIOUX CITY AREA
CLIMATIC SUMMARY
1999

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

 

...WET SPRING AND SUMMER...DRY THE REST OF 1999 AT SIOUX CITY...  

The total precipitation at Sioux City airport in 1999 was 29.45 inches which was 3.59 inches above normal. Almost all of this precipitation or 25.64 inches occurred in the 5 month growing season period from April through August...with only 3.81 inches recorded the remaining 7 months of 1999. The average temperature for 1999 was exactly 50.0 degrees or 1.5 degrees above the yearly normal.

1999 started out rather snowy and cold with 5.6 inches snowfall on January 1st to 2nd. 20 to 40 mph northwesterly winds caused blowing and drifting snow and low wind chills in the area through the 3rd. The lowest temperature of 1999 of 20 degrees below zero occurred on January 9th. Temperatures recovered nicely for February averaging 8.9 degrees above normal for the month. The warmest temperature of the month of 68 degrees on February 10th was a record for the date.

Snow returned to Sioux City on February 22nd with an 8.0 inch snowstorm for the biggest snowfall of 1999. Another 7.6 inches snow fell on March 8th and the total snowfall for the 1998 to 99 winter season ended up at 38.1 inches or 6.3 inches above average.

The rainy season started in April and continued through August with a number of severe weather and heavy rain events in the area... including the following...

May 22nd...around 540 pm thunderstorm winds gusting up to 60 mph damaged power lines and a few trees from Sioux City to Sergeant bluff.

June 4th...1.88 inches rain occurred at Sioux City airport in the early morning.

June 9th...thunderstorm winds gusted to 69 mph at the airport around 7 pm for the strongest wind measured for 1999.

June 15th...1.75 inches rain fell at the airport during the morning.

July 2nd...severe and heavy thunderstorms struck the Sioux City area between 4 and 6 am. First around 4 am large hail damaged vehicles and crops with hail drifting to 1 to 2 feet just east of Sioux City. Then a flash flood was caused by 3 or more inches of rain in less than an hour. Many basements were flooded and left with mud and debris. Some foundations and basement walls collapsed in Sioux City. Many roads were flooded...at one intersection to a depth of 8 feet... damaging vehicles by the water and debris. The flooding brought down some trees...and damaged some of the flooded streets as water undercut them. A motorist caught in the flooding and the firefighter who rescued him were treated at a hospital for hypothermia. The flooding caused crop damage in the countryside.

July 18th...1.68 inches rain fell at the airport in the early morning.

August 29th...flash flooding of urban areas and at least one stream resulted when 2 to 5.5 inches of rain fell from the south side of Sioux City to Salix between 8 and 10 pm. Officially at the airport 2.78 inches fell for the heaviest rain event there for 1999. Roads and low areas were flooded...basement flooding occurred...and a retaining wall collapsed.

The warmest temperature of 1999 was 96 degrees on both July 8th and July 29th. On July 29th the heat index rose to an incredible 119 degrees with a sultry dewpoint of 83 degrees.

The September to November period was the 3rd driest autumn on record ...totaling only 1.41 inches compared to a normal of 5.90 inches for the period. It was the warmest November on record...averaging 7.8 degrees above normal. Because of the unusually dry and warm weather and the favorably wet growing season...there was abundant grass and vegetation for fire problems in the area...and the air was often smoky and dusty. December 1999 continued the mild dry pattern averaging 7.0 degrees above normal.

Several daily record high temperatures were recorded at Sioux City from late October to December...86 degrees on October 27th...81 degrees on November 8th...73 degrees on November 9th...78 degrees on November 13th...and 61 degrees on December 29th.

THE FOLLOWING TABLES GIVE A MONTH BY MONTH BREAKDOWN OF WEATHER IN 1999 AT THE SIOUX CITY AIRPORT...

TEMPERATURES

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

JANUARY 27.3 10.4 18.9 PLUS 1.2 41 20B
FEBRUARY 41.8 23.1 32.5 PLUS 8.9 68 4
MARCH 48.8 25.2 37.0 PLUS 1.2 77 12
APRIL 59.3 39.1 49.2 MINUS 1.0 79 23
MAY 72.4 50.3 61.4 MINUS 0.2 87 37
JUNE 78.4 58.6 68.5 MINUS 2.3 94 43 4TH WETTEST
JULY 88.2 67.2 77.7 PLUS 2.0 96 53
AUGUST 82.1 59.6 70.9 MINUS 1.9 90 50
SEPTEMBER 75.0 47.0 61.0 MINUS 2.4 87 29
OCTOBER 66.5 34.4 50.5 MINUS 1.3 86 18
NOVEMBER 58.1 30.2 44.2 PLUS 7.8 81 19 1ST WARMEST
DECEMBER 40.0 17.5 28.8 PLUS 7.0 61 6B

1999 61.5 38.6 50.0 PLUS 1.5 96 20B

NORMAL YEAR 59.2 37.7 48.5

PRECIPITATION (INCHES) AND WINDS

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

JANUARY .33 MINUS .22 7.3 PLUS 0.9 NW 44 ON 18TH
FEBRUARY .81 PLUS .10 13.6 PLUS 7.9 NW 56 ON 11TH
MARCH .89 MINUS 1.07 9.4 PLUS 1.9 S 53 ON 30TH
APRIL 4.66 PLUS 2.32 0.8 MINUS 0.5 E 54 ON 8TH
MAY 5.21 PLUS 1.54 0 NW 56 ON 22ND
JUNE 7.90 PLUS 4.19 0 S 69 ON 9TH
JULY 3.30 PLUS .03 0 NE 56 ON 2ND
AUGUST 4.57 PLUS 1.60 0 NW 38 ON 12TH
SEPTEMBER .52 MINUS 2.36 0 NW 39 ON 8TH
OCTOBER .24 MINUS 1.70 T MINUS 0.9 NW 39 ON 22ND
NOVEMBER .67 MINUS .41 1.5 MINUS 1.8 N 47 ON 1ST
DECEMBER .35 MINUS .43 4.6 MINUS 2.1 N 40 ON 27TH

1999 29.45 PLUS 3.59 37.2 PLUS 5.4 S 69 JUNE 9TH

RICHARD S. RYRHOLM...CLIMATIC FOCAL POINT

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