Big Sioux River at Sioux City, IA
River level and flood forecast · Woodbury County
Normal10.0 ftas of Mon 2:30 PM
The river is 22.0 ft below flood stage (32 ft).
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 | 41 ft |
| Moderate flood stage | 38 ft |
| Flood stage | 32 ft |
| Action stage | 29 ft |
| Record crest (June 23, 2024) | 44.9 ft |
What floods at each level
From the National Weather Service, highest first.
- 48 ftThe levees on the South Dakota side are overtopped.
- 45.5 ftMore significant levee overtopping occurs in the Iowa Riverside Community with numerous homes and buildings flooded.
- 43 ftThe lower levees in the Iowa Riverside community are in danger of being overtopped if not sandbagged. This may result in flooding of several homes on either side of Dacotan Ave.
- 38 ftMost of the storm drains are submerged.
- 37 ftSeveral structures south of River Dr on the SD will flood if a levee failure occurs.
- 35 ftSome lower portions south of River Dr on the SD may be at risk of flooding with a levee failure.
- 32 ftAgricultural land north of the leveed area begins to flood.
Highest crests on record
- 44.9 ft — June 23, 2024
- 37.7 ft — June 20, 2014
- 37.46 ft — March 17, 2019
- 31.57 ft — June 25, 2018
- 21.89 ft — April 2, 2020
Recent crests: 13.27 ft (July 8, 2025) · 44.9 ft (June 23, 2024) · 18.57 ft (April 15, 2023) · 14.94 ft (June 2, 2022) · 12.37 ft (September 1, 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 (SXCI4); flow from the U.S. Geological Survey. Readings are provisional. In a flood, follow your local officials and the NWS at weather.gov.