Flood — Day, South Dakota

2025-08-13 to 2025-08-14 · near Roslyn, Day, South Dakota

Event narrative

Heavy rain caused water to run over South Dakota Highway 27 one mile south of Pierpont. Water was also reported over 422nd ave, 3 miles east of Pierpont, where a vehicle hydroplaned into the ditch. One of the rural county roads 5 miles southeast of Pierpont was partly washed out. Roadside ditches were full across the better part of northwest and north central Day county, with water overtopping several additional roads. 3.6 inches of rainfall was measured 6 miles east southeast of Pierpont by a resident, while a trained spotter 1 mile south of Roslyn recorded 4.64 inches. A resident 7 miles west of Roslyn would go on to estimate they received 5 inches of total rainfall.

Wider weather episode

Two clusters of storms would move across the forecast area on the 13th into the early morning hours of the 14th. The day started with an isolated stronger storm generating 1 inch hail 6 miles north northeast of Lowry. That cluster would continue to move east and intensify, with 1.5 inch hail observed 8 miles east of Pierpont. These storms would damage siding and crops around Pierpont, with additional thunderstorm wind damage to trees in the town of Roslyn.

Another cluster of storms would move through central South Dakota, with a peak wind gust of 73 mph recorded by the South Dakota State University mesonet station 12 miles south of Vivian. As this cluster departed and weakened, additional winds were generated, with a gust of 68 mph 3 miles southeast of Reliance on a South Dakota Department of Transportation mesonet station.

A total of 3.6 inches was observed 6 miles east southeast of Pierpont. This rainfall, on top of already saturated soils from the previous month's heavy rains, resulted in water over roads, a partial washout, and at least one stranded vehicle in this area. In Roslyn, a trained spotter recorded 4.64 inches.

View location on OpenStreetMap → (45.5900, -97.4000)

Source: NOAA Storm Events Database, event_id 1290362. Narrative written by the NWS forecast office that issued the report.