Lyon County

Every recorded tornado

1. Injuries and deaths are for the tornado’s whole path, which may extend beyond the county. Deaths recorded within Lyon County: 1.
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. Jun 20, 2024Flood$13.2 million
   National Weather Service narrative

   Rainfall amounts across Lyon County from June 20-22 ranged from 7 to 12 inches. Widespread overland flooding ensued with additional major to record flooding along the Big Sioux, Rock, and Little Rock Rivers, and Mud Creek. ||At the peak of flooding, approximately 50 people were evacuated from Rock Rapids, Doon, and Alvord. In Rock Rapids, there were 12 swift water rescues when flood waters overwhelmed the city. County-wide 605 homes were impacted by flood waters, 15 of which were declared a total loss. In addition, six businesses were declared a total loss. Reported damage to individual property is estimated to cost 2.7 million dollars. ||County infrastructure was also severely…

2. Apr 9, 2013Winter Storm, Lyon$5.0 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 6 inches at Rock Rapids. Many branches, limbs, whole trees, and power lines were downed by the weight of ice and accompanying wind. 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 made travel impossible in many areas, resulting in…

3. Jun 12, 2001Flash Flood$4.0 million
   National Weather Service narrative

   Very heavy rain caused flash flooding, forcing streams including the Kanaranzi River, Rio Grand, and Moon Creek to overflow and flood homes, garages, and storage sheds in George. Flooding of roads and other lowlands was widespread. A road washed out and at least four bridges were damaged in George.

4. Jun 15, 2014Flood$2.0 million
   National Weather Service narrative

   Repeated heavy rains caused record flooding of the Rock River. Numerous homes, businesses, roads, farmland, and other low areas were flooded, forcing many people to evacuate their homes and rely on Red Cross and other volunteer assistance for several days. The flooding was especially severe in Rock Rapids, where the river crested at a record 13.98 feet above flood stage on June 17th.

5. Mar 13, 2019Flood$1.9 million
   National Weather Service narrative

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

6. Jun 25, 2010Tornado$500,000
   National Weather Service narrative

   A tornado destroyed two hog confinement buildings, killing about 12 hogs, numerous outbuildings, a metal farm building, tore the roof off a house and damaged at least 6 other houses, and caused damage to other farm buildings, power lines, vehicles, and trees, before moving out of Lyon County and into Osceola County.

7. Aug 28, 2021Hail$300,000
   National Weather Service narrative

   Multiple pictures received of very large hail around Larchwood. Hail size ranged from tennis ball to as much as 4 inches in diameter. Several cars and houses reported to have all windows broken out. Property damage costs are a rough estimate.

8. Jan 28, 2023Winter Weather, Lyon$250,000
   National Weather Service narrative

   Snowfall totaled 5.0 inches in George. The roof of the community center in Inwood collapsed from the accumulated weight of snowfall over the past month.

9. Aug 17, 2019Tornado$200,000
   National Weather Service narrative

   A tornado touched down 5 miles west of Rock Rapids, just east of Fig Avenue north of 160th Street, marked by damage to a corn field. The tornado traveled in a general east-southeast direction, striking a farmstead and flattening a silo within the first half-mile of its track. Within another minute, the tornado slashed through another farmstead, causing significant damage to a grain bin, large trees, and removed roofing from a home and a livestock shed. Around three miles west-southwest of Rock Rapids, several power transmission poles were broken. As the tornado passed just south of Rock Rapids, damage was mainly to trees, with several uprooted. The final structural damage occurred…

10. Jan 17, 1996Ice Storm, Lyon$150,000
    National Weather Service narrative

    Freezing rain caused severe icing of roads and damage to trees and power lines. Indirect damage occurred because of power failures, including broken pipes. Strong winds following the freezing rain added to the damage. Very cold wind chill readings forced those without power and heat to seek other shelter.

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

111°F2 times, most recently Jul 17, 1936

All-time low

−40°F2 times, most recently Jan 12, 1912

Warmest night

84°FJul 12, 1893

Coldest day

−28°FFeb 8, 1899

Wettest day

6.41 in2 times, most recently Jun 22, 2024

Snowiest day

18.0 inFeb 18, 1962

Hottest year

1931mean 51.3°F

Coldest year

1917mean 42.4°F

Wettest year

201845.34 in

Driest year

197410.35 in

Snowiest season

79.5 in1961-62

Station Rock Rapids (USC00137147), 1,347 ft elevation, 4.2 miles from the population centre. Daily records from 1893 to October 27, 2026; 98.9% 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 USC00137147.
• 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.