About this river
Illinois River is a 21.2 mile river near Kayak Starved Rock in Illinois. Streamflow is measured at the USGS gauge Illinois River at Henry, IL (site 05558300). The National Hydrography Dataset places it at stream order 9. Reach geometry comes from the USGS National Hydrography Dataset.
Typical flow by month
1982 to 2026
Illinois River typically runs highest in April, at a median 19,350 cfs, and lowest in September, at 6,465 cfs. The highest flow on record for any single day is 149,000 cfs, in 2013.
| Month | Typical (cfs) | Usual range (cfs) | Relative level |
|---|---|---|---|
| January | 10,300 | 7,290 to 18,600 | |
| February | 12,300 | 7,770 to 19,400 | |
| March | 19,000 | 13,900 to 28,400 | |
| April | 19,350 | 13,000 to 29,000 | |
| May | 17,600 | 11,400 to 27,100 | |
| June | 16,250 | 9,790 to 24,950 | |
| July | 10,400 | 7,280 to 17,900 | |
| August | 7,360 | 5,610 to 10,200 | |
| September | 6,465 | 4,660 to 10,150 | |
| October | 6,640 | 4,750 to 11,600 | |
| November | 9,545 | 6,275 to 14,500 | |
| December | 11,100 | 6,350 to 17,800 |
Typical is the median of each month’s daily median values, and the usual range runs from the median 25th to the median 75th percentile, across about 45 years of record. Statistics published by the US Geological Survey for Illinois River at Henry, IL (site 05558300). Conditions on any given day can fall well outside the usual range. Check the current reading before you go.
Embed this gauge on your site
Paste this snippet anywhere, an outfitter page, a club site, a trip report, to show Illinois River's live streamflow, water level and 7-day trend. It reads the USGS gauge directly, updates itself, and links back here.
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