41 flood insurance claims·$329,139 paid·10 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 Grant County, South Dakota. 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 and flash flooding from summer thunderstorms dominate the flood risk profile in Grant County, South Dakota. Over the last 30 years, the NOAA Storm Events Database recorded 29 standard floods, 14 flash floods, and one lakeshore flood, resulting in a total of one death. Severe weather events, such as heavy rainfall from multiple thunderstorms in June 2025, brought over three inches of rain to areas near Milbank and Ortley, washing out roads, threatening home foundations, and causing the North Fork of the Whetstone River to overflow. Another low-pressure system brought additional rounds of heavy rain in June 2025.
Federal flood insurance claims data shows that flood risks extend across multiple zones. Properties in Zone X accounted for 19 claims with an average payout of $11,046 and an average recorded water depth of 5 inches. Properties in Zone A recorded 17 claims with an average payout of $7,260 and an average water depth of 11 inches. Additionally, claims were filed in Zone UNKNOWN (3 claims averaging $9,423 and 0 inches of recorded water depth) and Zone X_UNSHADED (2 claims averaging $391 and 2 inches of water depth). Homeowners, real estate agents, and journalists should pay the most attention to properties located near rivers, streams, and low-lying areas prone to heavy runoff and flash flooding during severe thunderstorm activity.
Summary written from NOAA storm reports and NFIP claims for this county. Not a prediction.
In flood insurance claims here that reported a flood depth, the average was 9 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 1997, with 12 claims and $181,476 paid, the year of Severe Winter Storms and Blizzard Conditions and Severe Flooding, Sever Winter Storms,heavy Rains High Winds.
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.
21 NOAA storm reports from Grant County describe what happened, in the words of the forecasters who covered it. Read the South Dakota flood stories →
22 federal disaster declarations since 1969, 10 of them floods, coastal storms or hurricanes.
| Disaster | Began |
|---|---|
| Flooding | Apr 9, 2023 |
| Severe Storm, Straight-line Winds, Tornadoes, And Flooding | May 12, 2022 |
| Severe Winter Storm, Snowstorm, And Flooding | Mar 13, 2019 |
| Severe Winter Storm | Dec 24, 2016 |
| Severe Storms, Tornadoes, And Flooding | Jun 19, 2013 |
| Flooding | Mar 11, 2011 |
| Flooding | Mar 10, 2010 |
| Severe Winter Storm | Jan 20, 2010 |
Weather and water disasters only; most recent first. Source: OpenFEMA Disaster Declarations.
44 since 1996: 14 flash floods, 29 river or area floods and 1 coastal floods or surges.
| Event | Date | Damage |
|---|---|---|
| Flood | Jun 26, 2025 | — |
| Flood | Jun 25, 2025 | — |
| Flood | Jun 13, 2025 | — |
| Flood | Aug 6, 2025 | — |
| Flood | May 7, 2024 | — |
| Flood | Apr 12, 2023 | — |
| Flood | Apr 11, 2023 | — |
| Flood | Apr 10, 2023 | $150,000 |
— = no damage estimate in the record. Source: NOAA Storm Events Database.
Flood · Jun 26, 2025. On June 25th, multiple thunderstorms from the morning into the early afternoon caused flooding in parts of northeast South Dakota. A CoCoRaHS observer 4 miles south-southeast of Milbank recorded 3.33 inches of rain, while the COOP observer in Milbank measured 3.25 inches. Grant County Emergency Management sent photos of washed-out roads, and a resident near Ortley documented water reaching a home's foundation.||Th…
Flood · Jun 25, 2025. On June 25th, multiple thunderstorms from the morning into the early afternoon caused flooding in parts of northeast South Dakota. A CoCoRaHS observer 4 miles south-southeast of Milbank recorded 3.33 inches of rain, while the COOP observer in Milbank measured 3.25 inches. Grant County Emergency Management sent photos of washed-out roads, and a resident near Ortley documented water reaching a home's foundation.||Th…
Flood · Jun 13, 2025. A broad low-pressure system brought several rounds of rain and a few strong, isolated thunderstorms to northeast South Dakota. The rain began on the morning of June 12th. A break in the rain mid-day allowed the atmosphere to destabilize, which led to stronger storms in the afternoon. One storm produced penny-sized hail 3 miles west of Blunt. Another storm in Mansfield produced penny to nickel-sized hail and winds…
Flood · Aug 6, 2025. Heavy thunderstorm rainfall of 2 to 4 inches on saturated soils resulted in flooding of the North Fork Whetstone River near Milbank late on the evening of August 6th.
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 Grant 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.