Flash Flood in Sioux County, Iowa

Flash Flood July 29, 2025 – July 30, 2025 · Sioux County, Iowa

Where the report was made, with tornadoes recorded within 15 miles over the years.

What the National Weather Service wrote

Runoff from heavy rainfall caused the Floyd River at Alton to rise 5 feet in less than 3 hours, resulting in a brief period over flood stage.

The wider storm

Thunderstorms erupted within a very moist and unstable environment across central South Dakota during the afternoon of July 29 in response to an approaching upper level short-wave from Colorado. These thunderstorms quickly grew upscale into a line, producing 55 to 75 mph wind gusts across southeast South Dakota and extreme northeast Nebraska, resulting in isolated tree damage. In addition, prolonged heavy rain resulted in some localized flash flooding across northwest Iowa.

Began near Alton (42.9867, -96.0029).

Source: NOAA Storm Events Database, event 1288623. Narratives are written by the National Weather Service forecast office that issued the report.

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