Lyon County, IA Environment & Hazard Risk
Very Low natural hazard risk, led by hail. 724 storm events since 1996.
- Expected yearly loss
- $10.89M
- Very Low nationally
- Storm events since 1996
- 724
- Most often hail
- Flood insurance policies
- 39
- 0.7% of homes
- Hurricanes nearby
- 0
- Since 1851
Natural hazard risk
FEMA National Risk Index, December 2025
Overall risk
Very Low
Score 19.2 of 100
Social vulnerability
Very Low
Score 10.6 of 100
Community resilience
Relatively High
Score 79.4 of 100
Community resilience runs the other way: a higher rating means a community can recover faster.
Building value exposed: $3.97B · Agriculture value exposed: $1.19B · Risk-adjusted yearly loss: $7.41M
Risk by hazard
- HailRelatively Moderate$2.53M/yr expected annual loss, about 6.1 events a year
- DroughtRelatively Moderate$906K/yr expected annual loss, about 20 events a year
- Winter weatherRelatively Moderate$209K/yr expected annual loss, about 18 events a year
- Ice stormRelatively Moderate$303K/yr expected annual loss, about 1.2 events a year
- TornadoRelatively Low$1.66M/yr expected annual loss, about once every 2 years
- Cold waveRelatively Low$1.08M/yr expected annual loss, about 8.6 events a year
- LandslideVery Low$615/yr expected annual loss, about once every 15 years
- Heat waveVery Low$206K/yr expected annual loss, about 5.1 events a year
- WildfireVery Low$19.69K/yr expected annual loss, about once every 1,933 years
- Strong windRelatively Low$248K/yr expected annual loss, about 4.2 events a year
- LightningVery Low$46.52K/yr expected annual loss, about 39 events a year
- EarthquakeVery Low$11.05K/yr expected annual loss, about once every 2,762 years
Bars show the national percentile score (0 to 100) for each hazard. Dollar figures are expected annual losses to buildings, people and crops. Not rated here: avalanche, coastal flooding, hurricane, riverine flooding, tsunami, volcanic activity.
Flood risk and insurance
National Flood Insurance Program and FEMA flood maps
Check the flood zone for an address
- Homes with flood insurance
- 39 of 5,408 (0.7%)
- Homes in high-risk flood zones
- 0
- Flood claims since 1978
- 75
- Claims paid since 1978
- $1.68M
Flood claims paid per year
- Iowa Flooding$236K · 8 claims
- June Midwest Flooding$185K · 5 claims
- Midwest Flooding$21.98K · 8 claims
Storm history
Since 1996: 724 events, 0 deaths, $46.46M in damage
- Hail167
- Winter Weather111
- Thunderstorm Wind97
- Flood89
- Drought42
- Winter Storm38
- Blizzard28
- High Wind24
- Tornado23
- Excessive Heat19
Events per year
43 tornadoes on record (EF0 7, EF1 6, EF2 1, F0 12, F1 10, F2 5).
Most damaging storms
Since 1996, ranked by deaths, injuries and damage
- Flood06/20/2024
Beloit, Lyon County
$13.2M damage
What happened
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 impacted. Nearly all gravel roads had some type of washout and 12 county bridges were impacted by flood waters. Preliminary damage assessments estimate damage to public infrastructure to be 10.5 million dollars. ||The majority of overland flooding subsided by June 25, but river flooding continued through the end of the month. For additional information on river flooding, please see other flood entries for Lyon County.
- Drought10/01/2023
Lyon
$5.5M damage
What happened
Severe (D2) drought conditions persisted through the month. Crop damage is an estimate from insured losses. Information provided by the United States Department of Agriculture.
- Drought10/18/2022
Lyon
$5.43M damage
What happened
Despite near normal temperatures, precipitation at Rock Rapids was around 10 percent of normal during October. Severe (D2) drought conditions developed mid-month. Crop damage is an estimate from insured losses. Information provided by the United States Department of Agriculture.
- Winter Storm04/09/2013
Lyon
$5M damage
What happened
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 schools and businesses being forced to close.
- Flash Flood06/13/2001
George, Lyon County
$4M damage
What happened
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.
- Flood06/01/2019
Beloit, Lyon County
$3.98M damage
What happened
During crop planting season, prolonged flooding led to the loss of or inability to plant crops across the area. Crop loss estimates provided by the United States Department of Agriculture.
Latest storm reports
Newest first
- Thunderstorm Wind52 kt wind07/26/2026
Rock Rapids, Lyon County
- Thunderstorm Wind60 kt wind07/26/2026
Rock Rapids, Lyon County
- Thunderstorm Wind56 kt wind07/26/2026
Rock Rapids Muni Arp, Lyon County
- Thunderstorm Wind55 kt wind07/26/2026
Larchwood Arpt, Lyon County
- Thunderstorm Wind54 kt wind07/26/2026
Rock Rapids, Lyon County
- Thunderstorm Wind74 kt wind07/26/2026
Inwood, Lyon County
- Thunderstorm Wind61 kt wind07/26/2026
Inwood, Lyon County
- Heat07/20/2026
Lyon
Drinking water
12 community water systems serve about 12,196 people. Violations since 2021.
None of the systems serving this county had a health-based violation in this period.
- Rock Rapids Municipal Water WorksServes 2,611 · Groundwater · Local governmentNo health violations
- Lyon-Sioux Rws-DoonServes 1,765 · Groundwater · PrivateNo health violations
- Lyon-Sioux Rws-Big SiouxServes 1,530 · Groundwater · PrivateNo health violations
- Lyon-Sioux Rws-Rock RapidsServes 1,187 · Purchased groundwater · PrivateNo health violations
- George Water SupplyServes 1,082 · Groundwater · Local governmentNo health violations
- Inwood Water SupplyServes 928 · Purchased groundwater · Local governmentNo health violations+1 monitoring or reporting
- Larchwood Water SupplyServes 926 · Purchased groundwater · Local governmentNo health violations+1 monitoring or reporting
- Doon Water SupplyServes 619 · Purchased groundwater · Local governmentNo health violations+4 monitoring or reporting
Largest systems by population served. Monitoring and reporting violations mean required tests or notices were late or missing, not that the water was unsafe.
Climate
1991-2020 normals at Rock Rapids, 3.6 mi from the county center
Summer highs peak around 85°F in Jul and winter lows bottom out near 6°F in Jan. About 29.3 inches of rain falls in a typical year, with 34.9 inches of snow.
| Month | High | Low | Rain | Snow |
|---|---|---|---|---|
| Jan | 25°F | 6°F | 0.61 in | 6.0 in |
| Feb | 30°F | 10°F | 0.70 in | 7.3 in |
| Mar | 43°F | 22°F | 1.52 in | 5.6 in |
| Apr | 58°F | 34°F | 3.03 in | 3.5 in |
| May | 70°F | 47°F | 3.96 in | 0.1 in |
| Jun | 81°F | 58°F | 5.03 in | - |
| Jul | 85°F | 62°F | 3.59 in | - |
| Aug | 82°F | 59°F | 3.12 in | - |
| Sep | 75°F | 50°F | 3.24 in | - |
| Oct | 61°F | 36°F | 2.23 in | 0.4 in |
| Nov | 44°F | 23°F | 1.42 in | 3.6 in |
| Dec | 30°F | 12°F | 0.82 in | 8.4 in |
| Year | 46°F average | 29.3 in | 34.9 in | |
Pollution sites
0 Superfund sites and 0 toxic release facilities in Lyon County
No Superfund sites or toxic release facilities in Lyon County in our data.
Superfund sitesToxic release facilitiesEPA inspections and enforcementAir toxics cancer risk7 historic places
Frequently asked questions
- How risky is Lyon County for natural disasters?
- FEMA rates Lyon County very low for overall natural hazard risk, with expected losses of $10.89M a year. The highest-rated hazards are hail (relatively moderate), drought (relatively moderate), winter weather (relatively moderate).
- What storms are most common in Lyon County?
- Since 1996, NOAA recorded 724 storm events affecting Lyon County, most often hail (167), winter weather (111), thunderstorm wind (97).
- How many tornadoes have hit Lyon County?
- 43 tornadoes have been recorded in Lyon County since 1950.
- How many homes in Lyon County have flood insurance?
- 39 residential flood insurance policies are in force in Lyon County, covering about 0.7% of homes. The program has paid $1.68M on 75 claims here since 1978.
- What is the weather like in Lyon County?
- At Rock Rapids, average highs reach 85°F in Jul and lows fall to 6°F in Jan, with 29.3 inches of rain a year (1991-2020 normals).
Source: FEMA (National Risk Index, NFIP), NOAA (Storm Events, HURDAT2, Climate Normals), EPA · Last updated 08/01/2026 · Storm counts include events in forecast zones that touch the county. This product uses the FEMA OpenFEMA API, but is not endorsed by FEMA.