Based on NOAA Storm Events Database records from 1996 to 2025, these are the New Hampshire counties with the most recorded flood events. Grafton County tops the list with 270 events. The data includes river floods, flash floods, coastal flooding, and hurricane-related flooding.
| Rank | County | Total Events | River Floods | Flash Floods |
|---|---|---|---|---|
| 1 | Grafton County | 270 | 158 | 107 |
| 2 | Coos County | 138 | 74 | 60 |
| 3 | Carroll County | 123 | 81 | 38 |
| 4 | Rockingham County | 122 | 28 | 15 |
| 5 | Merrimack County | 113 | 81 | 30 |
| 6 | Hillsborough County | 98 | 44 | 51 |
| 7 | Cheshire County | 74 | 14 | 58 |
| 8 | Sullivan County | 59 | 34 | 24 |
| 9 | Belknap County | 43 | 15 | 26 |
| 10 | Strafford County | 28 | 14 | 11 |
Source: NOAA Storm Events Database (1996–2025).
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