Enter any address in Hamlin County, South Dakota to see its FEMA flood zone
Flash flooding from summer thunderstorms is the dominant flood character in Hamlin County. Between 1993 and 2023, NOAA Storm Events data recorded 51 flood events and 18 flash flood events. For example, intense rainfall on August 17, 2025, caused flooding across the county, with an estimated 3 inches of rain falling near Lake Poinsett. Another event on August 22, 2025, saw storms over areas already saturated from months of rainfall, leading to flooding along the Big Sioux River and its tributaries.
National Flood Insurance Program (NFIP) claims data from Hamlin County shows that properties in Zone X_Unshaded have experienced the most claims, with an average payout of $13,415 and an average water depth of 1.3 feet. Zone X also shows a significant number of claims. Homeowners in areas designated as Zone A, as well as those in Zone X_Unshaded and Zone X, should pay particular attention to flood risk.
Summary generated from NOAA storm narratives and NFIP claim data for this county. Not predictive.
26 NOAA storm reports from this county describe what happened, in the words of the meteorologists who were there.
Hamlin County, South Dakota has recorded 77 flood-related events since 1996 according to NOAA's Storm Events Database, including 18 flash floods and 51 river or area floods. The county has received 22 federal disaster declarations, 10 of which involved flooding or coastal storms. Enter any address above to check its FEMA flood zone designation.
FEMA Disaster Declarations (1969–2022)
Source: OpenFEMA Disaster Declarations Summaries.
| Declaration | Type | Date |
|---|---|---|
| Severe Winter Storms And Snowstorm | Winter Storm | Dec 12, 2022 |
| Severe Storm, Straight-line Winds, Tornadoes, And Flooding | Severe Storm | May 12, 2022 |
| Covid-19 | Biological | Jan 20, 2020 |
| Covid-19 Pandemic | Biological | Jan 20, 2020 |
| Severe Storms And Flooding | Flood | May 21, 2019 |
| Severe Winter Storm, Snowstorm, And Flooding | Flood | Mar 13, 2019 |
| Severe Winter Storm | Severe Storm | Dec 24, 2016 |
| Severe Storms, Tornadoes, And Flooding | Severe Storm | Jun 19, 2013 |
| Flooding | Flood | Mar 11, 2011 |
| Flooding | Flood | Mar 10, 2010 |
NOAA Storm Events Database (1996–2025)
Source: NOAA National Weather Service Storm Events Database.
| Type | Date | Damage |
|---|---|---|
| Flash Flood | Jun 28, 2025 | 0.00K |
| Flood | Jul 27, 2025 | 0.00K |
| Flood | Aug 22, 2025 | 0.00K |
| Flood | Aug 17, 2025 | 0.00K |
| Flood | Aug 6, 2025 | 0.00K |
| Flood | Aug 1, 2025 | 0.00K |
| Flood | May 23, 2024 | 0.00K |
| Flood | Jun 23, 2024 | 0.00K |
| Flood | May 8, 2024 | 0.00K |
| Flood | Jun 3, 2024 | 0.00K |
Flash Flood — Jun 28, 2025
A volatile atmospheric setup on the afternoon and evening of June 28th led to the development of several powerful supercell thunderstorms across far eastern South Dakota. These storms produced multiple tornadoes, including two that caused significant damage in Deuel County. The strongest tornado was rated as a high-end EF3. Storms also produced large hail and instances of flash flooding from he...
Flood — Jul 27, 2025
An afternoon thunderstorm developed near the town of Henry and very quickly spun up a violent tornado. This tornado would cause significant damage to a farmstead before dissipating. The storm would go on to produce large hail, up to the size of baseballs near Lake Kampeska, with numerous additional reports of golf-ball sized hail, in and around the city of Watertown. The Watertown Automated Sur...
Flood — Aug 22, 2025
Storms moved over portions of northeast South Dakota that had really no extra room for moisture from the preceding months of nearly constant rainfall. Thus, this moisture went straight into the Big Sioux and tributaries from the Watertown area down south to Castlewood. The COOP observer in Rauville would record 1.51 inches of rainfall pushing their monthly total up to 5.73 and a 3 month total o...
Flood — Aug 17, 2025
Brief but intense heavy rainfall from thunderstorms, on top of weeks of wet weather, resulted in additional flooding across Marshall, Hamlin, Codington, and Deuel counties starting on the 17th and persisting well into the 18th. An estimated 3 inches of rain fell in Lake Poinsett, while 1.63 inches was recorded by the COOP sensor 20 miles north northeast of Aberdeen, 1.62 inches was submitted b...
Flood — Aug 6, 2025
Heavy rainfall of 2 to 4 inches across Codington and Hamlin counties, falling on already saturated soils due to above normal precipitation through the spring and summer months, resulted in flooding of the Big Sioux River and its tributaries including Mud and Willow Creeks. Flooding would mainly be limited to low spots and agricultural lands, however.
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 Hamlin County, South Dakota:
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 Hamlin County, South Dakota 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.