River stage
Seneca, Illinois River
- River level
- 20.65 ft
- Status
- Below flood stage
- 7-day change
- -0.26 ft
- Recent high
- 24.04 ft
- Recent low
- 20.16 ft
Last reported 2026-10-13 | NWS SNAI2
- 30-day change
- +0.17 ft
- Average
- 21.26 ft
- Readings
- 122
- Data span
- 122 days
- Record crest
- 32.25 ft
In brief
The Illinois River at Seneca, IL read 20.65 ft on Oct 13, 2026, 5.35 ft below action stage. That is 0.17 ft higher than 30 days earlier.
Source: National Weather Service gauge SNAI2
Water 67 °F (20 °C) · 4 °F warmer than normal for this date
River level timeline
Stage threshold profile
Highest crests on record
| Rank | Crest | Date |
|---|---|---|
| 1 | 32.25 ft | 2020-05-19 |
| 2 | 32.16 ft | 2019-05-02 |
| 3 | 30.78 ft | 2018-02-21 |
Flood crests recorded at this gauge by the National Weather Service.
What happens at each level
- 25.00 ft
Water overtops low-lying banks in Seneca.
- 27.00 ft
Roadways at numerous marinas threatened along the river near Seneca.
- 28.00 ft
Old Stage Road is threatened near the Illinois and Michigan Canal between Seneca and Morris. Agricultural land is inundated north of the river near Seneca.
- 31.00 ft
Backwater causes Rat Run to overtop its banks near Main Street in Seneca.
- 31.50 ft
Old Stage Road is threatened just east of Seneca.
- 32.00 ft
IL-36 (Dupont Road) is threatened along the river near Seneca.
- 33.00 ft
Backwater causes Rat Run to threaten a few structures near Main Street in Seneca.
- 33.50 ft
Industrial structures are threatened along the river west of Seneca.
- 35.00 ft
River Road is threatened near IL-170 in Seneca.
- 35.50 ft
A few residences threatened near River Road and IL-170 in Seneca.
Written by the local National Weather Service forecast office for this exact gauge.
Frequently asked questions
Is the Illinois River flooding at Seneca?
No. The Illinois River at Seneca is at 20.65 ft, 5.35 ft below action stage.
What is the flood stage at Seneca?
Action stage 26 ft is the first threshold.
What is the highest the Illinois River has been at Seneca?
The highest crest on record is 32.25 ft, on 2020-05-19.
Is the Illinois River high or low right now at Seneca?
At 20.65 ft it is higher than 30% of readings over the last 122 days.
How warm is the water at Seneca, Illinois River?
The water temperature at Seneca, Illinois River is 67 °F (19.6 °C), measured 6:45 pm by USGS, which is 4 °F warmer than normal for this date over the past ten years. It has risen 0.6 °F in the last 24 hours.
Stage and flood information from the NOAA National Weather Service (gauge SNAI2); daily history from the U.S. Geological Survey (site 05543010). Last reading 2026-10-13. For flood safety decisions always follow official National Weather Service warnings.