Winnebago River at Mason City, IA
River level and flood forecast · Cerro Gordo County
Normal5.1 ftas of Mon 2:45 PM
The river is 4.9 ft below flood stage (10 ft).
Flow: 219 cubic feet per second (USGS).
The last 7 days and the forecast
NWS forecast issued Sun, Dec 31, 6 PM. Forecasts change as rain falls and as upstream water arrives.
Flood stages
| Major flood stage | 15.5 ft |
| Moderate flood stage | 14.5 ft |
| Flood stage | 10 ft |
| Action stage | 8 ft |
| Record crest (June 8, 2008) | 18.74 ft |
What floods at each level
From the National Weather Service, highest first.
- 20.5 ftWater affects the floodwall at the water treatment plant located at 13th St NE.
- 17.4 ftWater reaches bottom of railroad bridge east of Kentucky Ave bridge.
- 15 ftThis is the approximate top of levee protection. Levees run from the 12th St NE bridge to 9th St along the east bank and also from 8th St to 6th St and Hampshire St.
- 14 ftWater may flow over the city dikes.
- 12 ftWidespread flooding occurs along the river. Some backwater effects are possible along Willow Creek between downtown Mason City and the confluence with the Winnebago river.
- 11 ftSandbagging occurs on the dike from 12th St NE to Carolina St.
- 10 ftWidespread flooding occurs at city parks. Water reaches the underside of the 12th St NE bridge at the piers.
- 8 ftWater affects east and west city parks in the 12th St NE area.
- 7 ftWater affects low-lying areas along the river.
Highest crests on record
- 18.74 ft — June 8, 2008
- 15.7 ft — March 30, 1933
- 14.8 ft — March 27, 1961
- 14.67 ft — May 22, 2004
- 14.27 ft — April 11, 1965
Recent crests: 11.19 ft (August 19, 2025) · 10.98 ft (June 22, 2024) · 11.24 ft (February 27, 2023) · 10.91 ft (April 13, 2022) · 5.78 ft (August 28, 2021)
Up and down the river, and nearby
Not an official source. River levels, forecasts, flood stages and impacts are from the National Weather Service (MCWI4); flow from the U.S. Geological Survey. Readings are provisional. In a flood, follow your local officials and the NWS at weather.gov.