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Flood in Dewey County, South Dakota
34 floods and flash floods events in the NCEI Storm Events record, 1950 to 2026. Event types counted: Flood, Flash Flood, Coastal Flood, Lakeshore Flood.
NCEI notes that Storm Data is compiled from a variety of sources including the National Weather Service, other federal, state and local agencies, the media and the public; that property and crop damage figures are estimates; and that some events are recorded by NWS forecast zone rather than by county. FEMA notes that NFIP claim records are redacted and aggregated to protect the privacy of policyholders. Storm records through 30 Jun 2026.
NCEI records 34 flood events in Dewey County, South Dakota, between 1950 and 2026, spread over 14 years.
June is the busiest month, with 10 of the recorded events. The last 20 years account for 27 events against 7 in the 20 years before, a change that reflects reporting practice as much as weather.
The county holds 1% of the 3,390 flood events recorded in South Dakota; its 1.5 per 100 square miles compares with 4.5 statewide.
Compared with South Dakota
| Measure | Dewey County | South Dakota | US |
|---|---|---|---|
| Flood events since 1950 | 34 | 3,390 | 183,559 |
| Per 100 square miles | 1.5 | 4.5 | 5.2 |
| Per 10,000 residents | 64.8 | 37.9 | 5.5 |
| Deaths recorded | 0 | 10 | 2,961 |
| Busiest month | June | June | June |
By year
Seasonality
0Feb
1Mar
7Apr
3May
3Jun
10Jul
3Aug
5Sep
2Oct
0Nov
0Dec
0
Recorded events
All 34 events, most recent first. Magnitude is hail size, tornado rating or wind speed as recorded.
| Date | Event type | Magnitude | Property damage | Crop damage | Deaths | Injuries | Geography |
|---|---|---|---|---|---|---|---|
| 18 Sep 2025 | Flood | — | — | — | — | — | County |
| 18 Sep 2025 | Flood | — | — | — | — | — | County |
| 1 Jun 2019 | Flood | — | — | $2.9M | — | — | County |
| 1 May 2019 | Flood | — | — | — | — | — | County |
| 1 Apr 2019 | Flood | — | $199K | — | — | — | County |
| 26 Mar 2019 | Flood | — | — | — | — | — | County |
| 24 Mar 2019 | Flood | — | — | — | — | — | County |
| 12 Aug 2017 | Flash Flood | — | — | — | — | — | County |
| 22 Jul 2016 | Flash Flood | — | — | — | — | — | County |
| 20 Jun 2014 | Flood | — | — | — | — | — | County |
| 11 Mar 2014 | Flood | — | — | — | — | — | County |
| 17 Mar 2011 | Flood | — | — | — | — | — | County |
| 17 Jun 2010 | Flood | — | — | — | — | — | County |
| 16 Jun 2010 | Flash Flood | — | $100K | — | — | — | County |
| 15 Jun 2009 | Flash Flood | — | — | — | — | — | County |
| 15 Jun 2009 | Flash Flood | — | $10K | — | — | — | County |
| 13 Apr 2009 | Flood | — | — | — | — | — | County |
| 17 Mar 2009 | Flood | — | — | — | — | — | County |
| 9 Feb 2009 | Flood | — | — | — | — | — | County |
| 23 Jul 2008 | Flash Flood | — | — | — | — | — | County |
| 5 Jun 2008 | Flood | — | $500K | $100K | — | — | County |
| 5 Jun 2008 | Flood | — | $75K | — | — | — | County |
| 18 Aug 2007 | Flood | — | — | — | — | — | County |
| 17 Aug 2007 | Flash Flood | — | — | — | — | — | County |
| 17 Aug 2007 | Flash Flood | — | — | — | — | — | County |
| 12 Jun 2007 | Flash Flood | — | — | — | — | — | County |
| 12 Jun 2007 | Flash Flood | — | — | — | — | — | County |
| 10 Aug 2006 | Flash Flood | — | — | — | — | — | County |
| 3 May 2003 | Flash Flood | — | — | — | — | — | County |
| 3 May 1999 | Flash Flood | — | — | — | — | — | County |
| 11 Jul 1997 | Flash Flood | — | — | — | — | — | County |
| 1 Apr 1997 | Flood | — | — | — | — | — | Forecast zone |
| 21 Mar 1997 | Flood | — | — | — | — | — | Forecast zone |
| 21 Mar 1997 | Flood | — | — | — | — | — | Forecast zone |
Questions and answers
How many flood events has Dewey County had?
34 events in the NCEI Storm Events record between 1950 and 2026. Reporting of floods and flash floods became far more complete after 1996, so early decades undercount.
When was the last recorded flood event in Dewey County?
18 Sep 2025 (Flood). Records reach NCEI about 120 days after the month ends.
What was the most damaging flood event recorded in Dewey County?
The flood of 1 Jun 2019, with property damage estimated by NCEI at $0 and crop damage at $2.9M.
How does Dewey County compare with South Dakota for flood?
1.5 events per 100 square miles against 4.5 statewide; the county holds 34 of the state's 3,390 recorded events.
Provenance
NOAA NCEI Storm Events Database, yearly details files through 30 Jun 2026, public domain. County-recorded events plus zone-recorded events whose forecast zone is named for the county (marked "Forecast zone"). Population and area from the US Census Bureau (2021). Built 1 Oct 2026. See the methodology, the Flood hub and the county page.