Day County, South Dakota

What hazards hit Day County most?

The most frequent records are hail reports: 207 since 1961. 51% of its hail reports since 1961 fell in June and July. The rank column places the county among South Dakota's counties by days with a record per 1,000 square miles of land over each hazard's complete period.

Source: NOAA NCEI Storm Events Database (county and forecast-zone records attributed to the county; a zone record shows its own totals on each county it covers). Days: dates with at least one record of the hazard in the county. Ranks: days with a record per 1,000 square miles of land (Census Bureau 2024 Gazetteer), since 1950 for tornadoes, 1955 for hail and thunderstorm wind, 1996 for the rest.

How many tornadoes has Day County had?

NOAA records 33 tornadoes in Day County from 1953 to 2026, the strongest rated F2, with 0 deaths and 1 injury recorded in the county. That is 25th of 66 South Dakota counties by days with tornadoes per 1,000 square miles since 1950. A tornado that crossed a county line is counted in each county it touched, with the length of its path inside the county.

Counted as whole tornadoes rather than county records, the Storm Prediction Center's database holds 33 tornadoes whose track touched Day County since 1950 (NOAA's county records number 33, the same count); along their whole tracks they killed 0 people.

Map of the strongest tornado tracks in South Dakota.

Source: NOAA NCEI Storm Events Database, tornado records by county (path length in the county, maximum width); ratings as published: F scale before February 1, 2007, EF scale after. Whole-track figures: NOAA Storm Prediction Center tornado database (1950-2025). SPC severe weather database.

When was the last damaging storm in Day County?

The most recent record with damage, injuries or deaths is the April 12, 2023 flood ($291,000 in damage in 2025 dollars).

Many roadways were flooded, including 447th Avenue south of Waubay.
National Weather Service event narrative, NOAA Storm Events Database (search the full record, event 1097388)

Source: NOAA NCEI Storm Events Database; every record of 2025-2026 is listed, earlier ones when they caused deaths, injuries or $250,000 of damage (2025 dollars), and every tornado.

The deadliest and costliest records

A damage figure marked "step" is a record from before 1993: NOAA then filed damage by category, and the figure is the category as entered, in the dollars of that year, not an estimate of the loss.

Source: NOAA NCEI Storm Events Database: deaths and injuries direct and indirect; damage is property plus crops as estimated by the National Weather Service, converted to 2025 dollars.

Is it getting more frequent?

Records per decade for Day County's most frequent hazards. Counts rose everywhere after 1996, when NOAA began recording every event type, so compare decades within a hazard's complete period only (the shaded cells come before it).

Extreme cold in the 2010s: 23 records against 7 in the decade before, 23 of them forecast-zone records. High wind and dust storms in the 2020-26: 24 records against 8 in the decade before, 24 of them forecast-zone records. Cells marked z rose mostly through zone records. The local National Weather Service office files these once per forecast zone, so a change in how it draws its zones or splits a storm into records moves this count as much as the weather does; read it beside the Day County days with a record above.

Source: NOAA NCEI Storm Events Database, records per calendar decade; zone records from the CZ_TYPE field (Z).

What time of year?

51% of its hail reports since 1961 fell in June and July. The two busiest months are in violet.

Source: NOAA NCEI Storm Events Database, records by the month they began.

Federal disaster declarations for Day County

FEMA's register lists 25 declarations that include Day County: 22 major disasters, 3 emergencies and 0 fire management assistance declarations. Most were for severe storm (11) and flood (9).

Source: FEMA OpenFEMA Disaster Declarations Summaries (v2), declarations through October 2, 2026; one declaration is counted once however many areas it names. OpenFEMA dataset page.

How many floods has Day County had?

NOAA's Storm Events Database holds 39 flood or flash flood records for Day County from 1997 to 2025, on 34 days, with 0 deaths. By flood insurance claims since 1978 (OpenFEMA, as of September 8, 2026), Day County ranks 819th of 2,942 U.S. counties.

The National Flood Insurance Program has paid $4.2 million on 257 claims filed in Day County; the most in one year was 82 in 1999. Claims count insured losses only: uninsured flood damage is not in this file.

Source: FEMA OpenFEMA NFIP Redacted Claims, as of September 8, 2026; claims by year of loss, payments in the dollars of the year paid. OpenFEMA dataset page.

FEMA's modeled risk for Day County

FEMA's National Risk Index rates Day County Very Low overall, with an expected annual loss of $7.2 million. These are FEMA's model estimates of future loss from 18 hazards, not a count of what happened; they can differ from the record above.

Source: FEMA National Risk Index, county table, December 2025 release. FEMA's National Risk Index map.

Counties that share a border with Day County

1. Brown County 1,437
2. Spink County 865
3. Codington County 782
4. Day County 747
5. Roberts County 688
6. Clark County 678
7. Marshall County 621
8. Grant County 566

Source: U.S. Census Bureau county adjacency file; NOAA NCEI Storm Events Database, records since 1950. The Census Bureau's adjacency file.

Next

• Tornadoes in South DakotaEvery South Dakota tornado since 1950 and the counties with the most per square mile
• Hail in South DakotaThe state's hail reports, by county, year and month
• The South Dakota recordEvery hazard in the state, its deadliest events and its federal declarations
• FEMA's risk rating for each hazard in Day CountyThe hazard risk calculator: 18 hazards beside the county's record
• Download Day County's FEMA declarations (CSV)25 rows: every declaration that named the county, for your own analysis