75 flood insurance claims·$1.7M paid·6 federal flood & hurricane disasters
Share of the whole county outline, rivers and lakes included; parts FEMA hasn’t mapped count as zero.
Shaded areas are FEMA’s mapped flood hazard zones in and around Lyon County, Iowa. Zoomed out they are simplified; at street level the map switches to FEMA’s exact layer. Tap anywhere to check that spot, or search an address above.
River flooding from prolonged heavy rainfall dominates Lyon County, with 89 recorded flood events compared to 12 flash flood events over the last 30 years. Heavy rainfall totals of 5 to 10 inches from June 20 to 22, 2024, caused major to record flooding along area streams and rivers, devastating several communities with extensive overland flooding. Additionally, thunderstorms on June 20, 2024, produced rainfall rates of 2 to 4 inches per hour, with 24-hour totals reaching 6 to 12 inches across Lyon and northern Sioux counties.
National Flood Insurance Program records indicate that property damage occurs in multiple zones. Zone A accounts for 59 claims with an average payout of $26,978 and an average recorded water depth of 30 inches. Zone X accounts for 13 claims with an average payout of $28,911 and an average recorded water depth of 25 inches, while an additional 3 claims in unknown zones averaged $2,505 with an average water depth of 2 inches.
Homeowners, real estate agents, and journalists should pay the closest attention to properties located in Zone A and Zone X, where historical claims demonstrate significant average water depths and financial payouts from riverine and overland flooding.
Summary written from NOAA storm reports and NFIP claims for this county. Not a prediction.
Less than 1% of Lyon County’s flood insurance claims were on properties rated outside FEMA’s high-risk zones.
59 NFIP claims with a recorded rated flood zone, 1978 to date. The zone is the one FEMA used to rate that policy, which may not match today’s map. Source: OpenFEMA NFIP claims.
In flood insurance claims here that reported a flood depth, the average was 28 inches.
Drawn to scale against an 80-inch door. Even a few inches soaks flooring, the bottom of the drywall and anything plugged in near the floor.
Average of the depths reported on claims (zero and implausible values left out); FEMA’s record doesn’t say exactly where each depth was measured. Source: OpenFEMA NFIP claims.
The worst year was 2014, with 38 claims and $1.1M paid, the year of Severe Storms, Tornadoes, Straight-line Winds, and Flooding.
Bar height is scaled by square root so ordinary years stay visible next to the worst one. NFIP claims by year of loss. Source: OpenFEMA.
29 NOAA storm reports from Lyon County describe what happened, in the words of the forecasters who covered it. Read the Iowa flood stories →
16 federal disaster declarations since 1965, 6 of them floods, coastal storms or hurricanes.
| Disaster | Began |
|---|---|
| Severe Storms, Flooding, Straight-line Winds, And Tornadoes | Jun 16, 2024 |
| Severe Storms And Flooding | Mar 12, 2019 |
| Severe Storms, Tornadoes, Straight-line Winds, And Flooding | Jun 6, 2018 |
| Severe Storms, Tornadoes, Straight-line Winds, And Flooding | Jun 14, 2014 |
| Severe Storms, Tornadoes, And Flooding | May 19, 2013 |
| Severe Winter Storm | Apr 9, 2013 |
| Severe Storms, Flooding, And Tornadoes | Jun 1, 2010 |
| Severe Storms, Tornadoes, And Flooding | May 25, 2008 |
Weather and water disasters only; most recent first. Source: OpenFEMA Disaster Declarations.
101 since 1996: 12 flash floods and 89 river or area floods.
| Event | Date | Damage |
|---|---|---|
| Flood | Jun 21, 2024 | — |
| Flash Flood | Jun 21, 2024 | — |
| Flash Flood | Jun 20, 2024 | — |
| Flood | Jun 20, 2024 | $13.2M |
| Flood | Jul 1, 2024 | — |
| Flood | Apr 11, 2023 | — |
| Flood | Apr 10, 2023 | — |
| Flood | Mar 29, 2020 | — |
— = no damage estimate in the record. Source: NOAA Storm Events Database.
Flood · Jun 21, 2024. A multi-day significant heavy rainfall event from June 20-22 resulted in widespread rain totals between 5 and 10 inches across portions of southeast South Dakota, northwest Iowa, and southwest Minnesota. As rainfall reached area streams and rivers, major to record flooding was observed, devastating several towns and communities. Extensive overland flooding also resulted in significant impacts and damages. All rive…
Flash Flood · Jun 21, 2024. Clusters of thunderstorms with very high rainfall rates from 2 to 4 inches per hour developed by midday on June 20, and despite being transient, continued to redevelop through the evening and into the overnight hours. The primary focus occurred between Iowa Highway 9 and U.S. Highway 18 as the effective cold pool boundary collapsed southward and locked in place through the night. The final 24 hour rainfall totals…
Flash Flood · Jun 20, 2024. Clusters of thunderstorms with very high rainfall rates from 2 to 4 inches per hour developed by midday on June 20, and despite being transient, continued to redevelop through the evening and into the overnight hours. The primary focus occurred between Iowa Highway 9 and U.S. Highway 18 as the effective cold pool boundary collapsed southward and locked in place through the night. The final 24 hour rainfall totals…
Flood · Jun 20, 2024. A multi-day significant heavy rainfall event from June 20-22 resulted in widespread rain totals between 5 and 10 inches across portions of southeast South Dakota, northwest Iowa, and southwest Minnesota. As rainfall reached area streams and rivers, major to record flooding was observed, devastating several towns and communities. Extensive overland flooding also resulted in significant impacts and damages. All rive…
National Weather Service narratives, lightly trimmed. Source: NOAA Storm Events Database.
Every colour on the map above is a place on this drawing: where the ground sits relative to the flood FEMA plans for.
If a building in Lyon County is in a high-risk zone (A or V) and its mortgage comes from a federally regulated or insured lender, or is federally backed, flood insurance is required.
Outside those zones it is optional, and often worth having: from 2014 to 2024 nearly one-third of NFIP claims came from outside the high-risk Special Flood Hazard Area. Since Risk Rating 2.0, NFIP premiums are set for each building, so the only reliable price is a quote: FloodSmart.gov or a local agent.