Enter any address in Sioux County, Iowa to see its FEMA flood zone
Flash flooding from summer thunderstorms is the dominant flood character in Sioux County. Between 1993 and 2023, NOAA Storm Events data recorded 122 flood events and 41 flash flood events, resulting in one death. Recent examples include localized flash flooding across northwest Iowa following thunderstorms on July 29, 2025, and June 2, 2025.
National Flood Insurance Program (NFIP) claims data shows that properties in Zone A experienced an average of 2.5 feet of water depth with an average payout of $113,976. Properties in Zone X, including Zone X_Unshaded, also saw significant water depth averaging 3.0 feet, with Zone X claims averaging $111,341 and Zone X_Unshaded claims averaging $3,407. Homeowners in Zone A and those in Zone X with substantial water depth should pay the most attention to flood risk.
Summary generated from NOAA storm narratives and NFIP claim data for this county. Not predictive.
55 NOAA storm reports from this county describe what happened, in the words of the meteorologists who were there.
Sioux County, Iowa has recorded 163 flood-related events since 1996 according to NOAA's Storm Events Database, including 41 flash floods and 122 river or area floods. The county has received 15 federal disaster declarations, 5 of which involved flooding or coastal storms. Enter any address above to check its FEMA flood zone designation.
FEMA Disaster Declarations (1965–2024)
Source: OpenFEMA Disaster Declarations Summaries.
| Declaration | Type | Date |
|---|---|---|
| Severe Storms, Flooding, Straight-line Winds, And Tornadoes | Severe Storm | Jun 16, 2024 |
| Covid-19 | Biological | Jan 20, 2020 |
| Covid-19 Pandemic | Biological | Jan 20, 2020 |
| Severe Storms And Flooding | Flood | Mar 12, 2019 |
| Severe Storms, Tornadoes, Straight-line Winds, And Flooding | Severe Storm | Jun 6, 2018 |
| Severe Storms, Tornadoes, Straight-line Winds, And Flooding | Flood | Jun 14, 2014 |
| Severe Storms, Tornadoes, And Flooding | Severe Storm | May 19, 2013 |
| Severe Winter Storm | Severe Storm | Apr 9, 2013 |
| Severe Storms, Flooding, And Tornadoes | Severe Storm | Jun 1, 2010 |
| Severe Winter Storms And Snowstorm | Severe Storm | Dec 23, 2009 |
NOAA Storm Events Database (1996–2025)
Source: NOAA National Weather Service Storm Events Database.
| Type | Date | Damage |
|---|---|---|
| Flood | Jul 30, 2025 | 0.00K |
| Flash Flood | Jul 30, 2025 | 0.00K |
| Flash Flood | Jul 29, 2025 | 0.00K |
| Flood | Jun 2, 2025 | 0.00K |
| Flash Flood | Jun 2, 2025 | 0.00K |
| Flood | Jun 22, 2024 | 0.00K |
| Flood | Jun 21, 2024 | 0.00K |
| Flash Flood | Jun 21, 2024 | 0.00K |
| Flood | Jun 20, 2024 | 0.00K |
| Flood | Jun 20, 2024 | 6.50M (1 deaths) |
Flood — Jul 30, 2025
A wet period at the end of the July resulted in saturated soils and increased runoff, allowing for isolated river flooding through portions of the Floyd River Basin. The sharpest rises were observed with a heavy rain on the night of July 29 into the morning of July 30.
Flash Flood — Jul 30, 2025
Thunderstorms erupted within a very moist and unstable environment across central South Dakota during the afternoon of July 29 in response to an approaching upper level short-wave from Colorado. These thunderstorms quickly grew upscale into a line, producing 55 to 75 mph wind gusts across southeast South Dakota and extreme northeast Nebraska, resulting in isolated tree damage. In addition, prol...
Flash Flood — Jul 29, 2025
Thunderstorms erupted within a very moist and unstable environment across central South Dakota during the afternoon of July 29 in response to an approaching upper level short-wave from Colorado. These thunderstorms quickly grew upscale into a line, producing 55 to 75 mph wind gusts across southeast South Dakota and extreme northeast Nebraska, resulting in isolated tree damage. In addition, prol...
Flood — Jun 2, 2025
Locally heavy rainfall from thunderstorms resulted in quick, but brief rises on smaller creeks and streams in the immediate area. These elevated levels quickly fell back below flood stage as water moved downstream.
Flash Flood — Jun 2, 2025
Scattered strong to severe thunderstorms developed late afternoon along a slow-moving frontal boundary. Even with fairly weak deep-layer shear, strong instability resulted in large hail. Drier air and advancing cold pools later in development produced spotty damaging winds. High moisture content and slowly progressing storms also produced some locally heavy rainfall with rates briefly from 3 to...
Source: NOAA National Weather Service Storm Events Database.
Source: OpenFEMA NFIP Individual Claims (2.25M records analyzed).
FEMA assigns flood zone designations to areas in Sioux County, Iowa:
AE High Risk — 1% annual chance of flooding. Insurance required.
VE Very High Risk — Coastal flooding with wave action.
X (Shaded) Moderate Risk — 500-year floodplain.
X Low Risk — Outside major floodplains.
Properties in Sioux County, Iowa that are in FEMA-designated Special Flood Hazard Areas (zones A and V) with federally backed mortgages are required to carry flood insurance.
Even outside high-risk zones, flood insurance is recommended. From 2014 to 2024, nearly one-third of NFIP claims came from outside the high-risk Special Flood Hazard Area.
Visit FloodSmart.gov to find an agent and get a quote.