Sioux County

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond the county. Deaths recorded within Sioux County: 0.
2. Weak tornadoes were under-recorded before Doppler radar coverage became national in the early 1990s, so earlier decades read low. Ratings use the Fujita scale before February 2007 and the Enhanced Fujita scale after.

Storm Prediction Center severe weather database, 1950 to 2025.

Smoke overhead

1. A smoke day is a date on which a smoke plume traced by NOAA Hazard Mapping System analysts from satellite imagery covered this place's point (the county's population centre or the city centre). Counts here are of medium or heavy smoke. Since 2018 analysts have often drawn light smoke as one area over most of the continent, so light-smoke counts are not comparable from year to year. The plumes show smoke anywhere in the air above, not air quality at the ground, and smoke hidden by cloud is missed.

NOAA Hazard Mapping System smoke analysis, 2011 to 2026, retrieved October 30, 2026.

Claims by ZIP code

This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).

OpenFEMA NFIP Redacted Claims v3, refreshed August 4, 2026. NOAA Storm Events through 2026.

River crests

River gauges

1. Crests are the highest and the recent crests the National Weather Service lists for each river gauge in the county that has a flood stage, not every flood. Flood categories use each gauge's current flood stages; crests from before levees, dams or channel changes may not be comparable. Crests measured on an old datum are left out of the rankings.

NOAA National Water Prediction Service gauge records, retrieved October 30, 2026.

1. The Palmer Drought Severity Index is computed by NOAA each month from the county's average temperature and precipitation, relative to the county's own climate. Zero is normal; -3 or lower is severe drought and -4 or lower extreme drought. It describes the long-term balance of moisture, not water supply or crop losses.

NOAA NCEI nClimDiv county Palmer Drought Severity Index, 1895 to September 2026, issued October 6, 2026.

1. Earthquakes of magnitude 2.5 or more in the USGS Comprehensive Catalog since 1900. Within 50 miles means the epicentre lies within 50 miles of the county boundary (or inside the county).
2. Small earthquakes were under-recorded before the modern seismic networks of the 1970s and are still missed in remote areas, so early decades read low. Magnitudes are as the catalogue reports them and mix scales (moment, local and body-wave).

USGS ANSS Comprehensive Earthquake Catalog, 1900 to present, retrieved October 30, 2026.

More event types since 1996

Costliest events since 1996

1. Apr 9, 2013Winter Storm, Sioux$10.0 million
   National Weather Service narrative

   An extended period of precipitation began with freezing rain quickly producing heavy ice accumulations, ranging up to between a quarter and half inch. The precipitation then changed to sleet and then snow, with sleet and snow accumulations reaching 5 inches at Rock Valley. Many branches, limbs, whole trees, and power lines were downed by the weight of ice and accompanying wind, especially over the northern part of the county. Both urban areas and rural electric cooperatives suffered major power line damage. Trees and tree debris blocked many roads, and damaged several vehicles and homes. Major power outages were reported, affecting thousands of people. The winter precipitation…

2. Jun 20, 2024Flood$6.5 million
   National Weather Service narrative

   Rainfall amounts across Sioux County from June 20-22 ranged from 2 to 7 inches, with the highest amounts across the northern half of the county. Farther north and upstream, up to 12 inches of rain fell across portions of southeast South Dakota and northwest Iowa. This rainfall resulted in extensive overland flooding and major to record flooding along the Big Sioux, Rock, West Branch Floyd, and Floyd Rivers, and Burr Oak Creek. ||Large sections of Rock Valley and Hawarden were evacuated as flood waters inundated both cities. An estimated 200 people were rescued during the peak of the flooding. An estimated 60 businesses were impacted by flood water in Rock Valley and Hawarden.…

3. May 11, 2014Tornado$3.0 million
   National Weather Service narrative

   A tornado damaged 3 farmsteads in including damage to at least one house. The greatest damage was to structures and vehicles at a dairy farm.

4. Aug 5, 2023Flash Flood$1.5 million
   National Weather Service narrative

   Water ponding in the area of Central Park overflowed roadways and entered the Sioux Center Fire Department building. Two homes suffered the collapse of basement walls from the high water. Water also inundated a transformer which cut off power to seven homes in the northwest part of town. Seven trailers were evacuated due to high water in Westbrook Village on the northwest edge of town. More than two dozen vehicles were stranded in high water. Damage costs are rough estimates.

5. Jun 16, 2014Flood$1.0 million
   National Weather Service narrative

   Repeated heavy rains caused record flooding of the Rock River. Several homes, businesses, roads, farmland, and other low areas were flooded, forcing some people to evacuate their homes and rely on Red Cross and other volunteer assistance for several days. The flooding was severe in Rock Valley, where the river crested at a record 6.68 feet above flood stage on June 17th, and where a levee break added to flooding in the town.

6. Nov 12, 2005Tornado$800,000
   National Weather Service narrative

   A tornado destroyed the wall and part of the roof of a business in Hospers, and caused minor damage to contents in the building.

7. Mar 13, 2019Flood$610,000
   National Weather Service narrative

   Flooding resulted in extensive damage to public infrastructure including numerous county and township roads, culverts, and some bridges.

8. May 1, 2008Tornado$500,000
   National Weather Service narrative

   A tornado damaged numerous trees, including large trees uprooted, blew windows out of a home, destroyed a metal shed, blew two windows and part of a wall out of a metal building, damaged at least three grain bins, destroyed or damaged numerous outbuildings and small sheds, blew down or snapped off at least 15 power poles, bent a metal light pole, tipped one wagon and blew the top off another, blew down a barb wire fence and pushed fence posts almost to the ground, destroyed a hog barn, and flattened corn stubble, before crossing the county line into Lyon County. Contents inside several damaged or destroyed buildings and sheds were also damaged, especially on one farm where damaged…

9. Jun 15, 2014Flood$500,000
   National Weather Service narrative

   Repeated heavy rains caused record flooding of the Big Sioux River. Farmland and other lowlands including numerous roads were flooded, especially along the river in southwestern Sioux County, near and south of where the flooding Rock River empties into the Big Sioux. Some roads were damaged, and some secondary roads were washed out. Several homes and farm buildings were flooded and damaged. The river crested at a record 12.92 feet above flood stage at Hawarden on June 17th.

10. Jul 4, 2019Thunderstorm Wind$400,000
    National Weather Service narrative

    Downburst winds removed the roof and most walls from a home at the corner of 8th Avenue and 12th Street. Debris from this home damaged a downstream home toward the east. A utility pole and several trees were snapped off, which started a small fire. |Several other homes had some lesser collateral roof or siding damage within a three block stretch toward the east and southeast.

1. Storm Events records before 1996 cover only tornadoes, thunderstorm wind and hail. Damage figures are as reported by the National Weather Service at the time, not adjusted for inflation.

NOAA NCEI Storm Events Database, 1950 to 2026, issued October 26, 2026.

All-time high

109°F2 times, most recently Jul 17, 1936

All-time low

−37°FJan 12, 1912

Warmest night

81°FAug 18, 1936

Coldest day

−17°FJan 12, 1912

Wettest day

7.05 inAug 5, 2023

Snowiest day

12.0 in2 times, most recently Mar 2, 1977

Hottest year

2012mean 52.9°F

Coldest year

1924mean 41.9°F

Wettest year

201847.61 in

Driest year

195814.17 in

Snowiest season

73.2 in1982-83

Station Sioux Center 2 Se (USC00137700), 1,360 ft elevation, 1.9 miles from the population centre. Daily records from 1899 to October 26, 2026; 98.7% of days in the last 30 years are complete. Records at a single station can differ from a city’s official threaded record, which may combine several stations.

NOAA NCEI Global Historical Climatology Network Daily.

This product uses the Federal Emergency Management Agency's OpenFEMA API, but is not endorsed by FEMA. The Federal Government or FEMA cannot vouch for the data or analyses derived from these data after the data have been retrieved from the Agency's website(s).

OpenFEMA Disaster Declarations Summaries, retrieved October 30, 2026. Statewide declarations are not listed.

Neighbouring counties

• Tornadoes NOAA Storm Prediction Center severe weather database, through 2025.
• Tropical cyclones NOAA National Hurricane Center HURDAT2 (Atlantic; Northeast and Central Pacific), through 2025.
• Wildfire USGS/USFS Monitoring Trends in Burn Severity, through 2026.
• Storm events NOAA NCEI Storm Events Database, through 2026.
• Flood insurance OpenFEMA NFIP Redacted Claims v3, refreshed August 4, 2026.
• Declarations OpenFEMA Disaster Declarations Summaries v2, retrieved October 30, 2026.
• Weather records NOAA NCEI Global Historical Climatology Network Daily, station USC00137700.
• River crests NOAA National Weather Service, National Water Prediction Service river gauges, retrieved October 30, 2026.
• Drought NOAA NCEI nClimDiv county Palmer Drought Severity Index, through September 2026.
• Smoke NOAA NESDIS Hazard Mapping System smoke analysis, retrieved October 30, 2026.
• Earthquakes USGS ANSS Comprehensive Earthquake Catalog (ComCat), retrieved October 30, 2026.

Joins, thresholds and known limits are set out in the methodology. Found an error? Report it. Page built October 30, 2026.