SIOUX CITY AREA
CLIMATIC SUMMARY
1998

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

 

...OVERALL 1998 WAS A WARM AND WET YEAR IN SIOUX CITY...

 

Overall, 1998 was relatively warm and wet with the temperatures averaging 50.9 degrees or 2.4 degrees above normal...and precipitation totaling 30.77 inches at the Sioux City airport or 4.91 inches above average. The following is a chronological summary for 1998 for the Sioux City area...

The year started rather warm with the winter period of December... January...and February averaging out to 28.8 degrees...or 7.4 degrees above normal...the 4th warmest such period since records began in 1890. The month of February averaged 11.2 degrees above normal which tied February 1987 for the 4th warmest February on record.

The next 4 months were wet and wild overall. The low temperature of the year of 14 below zero was registered on March 14th...and also was a record low for the date. March was the 5th wettest march on record and April was the 5th wettest April. There were a number of record daily precipitation amounts... 1.03 inches on march 31st... 1.41 inches on April 7th... 1.03 inches on April 15th...and 2.09 inches on April 25th.

In May...severe weather made a number of appearances. Thunderstorm winds gusted to 77 mph at 1007 pm on May 11th for the strongest wind of the year...and to 68 mph at 1042 a.m. on May 15th. 1 to 1 3/4 inch diameter hail was reported at Sioux City from 720 to 810 pm on May 28th and also at 905 am on May 30th. In the climbing hill area east of Sioux City on the 28th widespread hail caused extensive damage to windows and crops from 855 to 915 pm. Severe weather also occurred the evening of June 23rd with a number of reports of hail...high winds...flash flooding...and small tornadoes in the area...especially south of Sioux City. Thunderstorm rainfall of 3 to 7 inches caused flash flooding in southern Woodbury County the night of the 23rd to 24th.

The summer of June...July...and august was somewhat below normal in temperature overall...but the rest of the year was above normal. The highest temperature of the year of 96 degrees was registered on September 19th and September averaged 6.7 degrees above normal for the 3rd warmest September on record. It was also very dry for the month with only 0.42 inch of precipitation. A rare event occurred at Sioux City the evening of September 25th. Strong winds gusting to 57 mph around 925 pm from dying thunderstorms caused a heat burst with temperatures rapidly warming into the 90s in the late evening. The winds also caused some tree and power line damage in the area.

The fall period of September...October...and November was the 5th warmest autumn on record. There were several strong low pressure systems to affect the area in October through early November that occasionally put a damper on the warm fall...especially the intense storm that moved through the area November 10th. This storm produced heavy snow north of Sioux City...a monthly record low barometric pressure of 28.85 inches...and strong west winds gusting to 62 mph. However the temperatures recovered nicely for the last half of November through the first half of December. Every day from November 21st through December 18th was well above normal with the 28 day period averaging 14.4 degrees above normal. Record high temperatures occurred on the following dates... 73 on November 27th... 63 on November 29th...70 on December 1st... 62 on December 2nd... 61 on December 3rd...and 59 on December 14th. The warm spell came to a halt December 19th and temperatures were generally below normal for the rest of the month.

THE FOLLOWING TABLES GIVE A MONTH BY MONTH BREAKDOWN OF WEATHER IN 1998 AT THE SIOUX CITY AIRPORT...

TEMPERATURES

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

JANUARY 30.6 15.7 23.2 PLUS 5.5 53 9B
FEBRUARY 42.1 27.4 34.8 PLUS 11.2 64 13 TIE 4TH
WARMEST
MARCH 38.1 23.0 30.6 MINUS 5.2 80 14B 5TH WETTEST
APRIL 62.3 38.1 50.2 0 82 25 5TH WETTEST
MAY 77.3 53.0 65.2 PLUS 3.6 94 40
JUNE 77.2 55.8 66.5 MINUS 4.3 92 43
JULY 84.8 64.3 74.6 MINUS 1.1 94 51
AUGUST 83.2 63.8 73.5 PLUS 0.7 92 55
SEPTEMBER 84.2 55.9 70.1 PLUS 6.7 96 42 3RD WARMEST
OCTOBER 65.8 42.5 54.2 PLUS 2.4 81 32
NOVEMBER 50.0 31.0 40.5 PLUS 4.1 73 22
DECEMBER 40.4 15.2 27.8 PLUS 6.0 70 8B

1998 61.3 40.5 50.9 PLUS 2.4 96 14B

NORMAL YEAR 59.2 37.7 48.5

PRECIPITATION (INCHES) AND WINDS

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

JANUARY .80 PLUS .25 5.7 MINUS 0.7 NW 39 ON 9TH
FEBRUARY .46 MINUS .25 3.0 MINUS 2.7 S 45 ON 25TH
MARCH 4.01 PLUS 2.05 11.5 PLUS 4.0 NW 44 ON 13TH
APRIL 6.06 PLUS 3.72 0.1 MINUS 1.2 S 52 ON 12TH
MAY 2.87 MINUS .80 0 S 77 ON 11TH
JUNE 5.67 PLUS 1.96 0 E 52 ON 8TH
JULY 1.49 MINUS 1.78 0 N 55 ON 21ST
AUGUST 3.55 PLUS .58 0 W 36 ON 14TH
SEPTEMBER .42 MINUS 2.46 0 SW 57 ON 25TH
OCTOBER 3.49 PLUS 1.55 0 MINUS 0.9 SE 39 ON 4TH
NOVEMBER 1.80 PLUS .72 2.0 MINUS 1.3 W 62 ON 10TH
DECEMBER .15 MINUS .63 5.0 MINUS 1.7 NW 45 ON 29TH

1998 30.77 PLUS 4.91 27.3 MINUS 4.5 S 77 MAY 11TH

RICHARD S. RYRHOLM...CLIMATIC FOCAL POINT

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