Flood in Jefferson County, Wisconsin

Flood April 18, 2026 – April 30, 2026 · Jefferson County, Wisconsin

$1K

Damage as recorded

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

What the National Weather Service wrote

The Rock River at Lake Koshkonong rose to Moderate flood stage. There was widespread flooding of roads and docks in the Town of Koshkonong and Town of Sumner including Vets Lane, Blackhawk Island Road and Oxbow Bend Road. There was knee-deep water over Blackhawk Island Road. Lamp Road on the west side of the river also became flooded. Lake Koshkonong merged with Mud Lake to the east of Lake Koshkonong.

The wider storm

There was extensive river flooding along the Wisconsin River, Fox River, and Rock River in southern Wisconsin in April. The river levels were above normal after 5 inches of rain fell over the 5 days, and then another episode of heavy rain of 3 to 5 inches occurred on April 17th. In addition, vegetation was still fairly dormant so the grass was not able to soak up much of the rainfall.

Began near Busseyville (42.9300, -88.9400).

Source: NOAA Storm Events Database, event 1332915. Narratives are written by the National Weather Service forecast office that issued the report.

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