Mississippi River at Grafton, IL: flow right now vs. normal
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—flow right now
—of typical for this month
—gage height
The Mississippi River at Grafton, IL gauge has averaged 114,150 cfs over 92 years of monthly records. Flow is usually highest in April (195,284 cfs) and lowest in September (72,461 cfs).
Typical flow by month
Highest in April (195,284 cfs), lowest in September (72,461 cfs).
Key figures
- Average flow
- 114,150 cfs
- Highest peak on record
- 598,000 cfs
- Year of that peak
- 1993
- Drainage area
- 171,300 sq mi
- Years of records
- 92
- Gauge elevation
- 403 ft
- River
- Mississippi River
- County
- Jersey
- State
- Illinois
Monthly numbers
| Month | Average | Median | Lowest | Highest |
|---|---|---|---|---|
| Jan | 72,633 cfs | 62,350 cfs | 22,700 cfs | 228,000 cfs |
| Feb | 81,681 cfs | 78,100 cfs | 24,900 cfs | 176,500 cfs |
| Mar | 145,751 cfs | 139,000 cfs | 39,600 cfs | 316,000 cfs |
| Apr | 195,284 cfs | 189,500 cfs | 62,000 cfs | 384,000 cfs |
| May | 191,886 cfs | 190,000 cfs | 42,100 cfs | 427,000 cfs |
| Jun | 164,879 cfs | 153,000 cfs | 31,550 cfs | 447,500 cfs |
| Jul | 133,242 cfs | 118,000 cfs | 30,200 cfs | 472,000 cfs |
| Aug | 79,914 cfs | 74,900 cfs | 22,000 cfs | 388,000 cfs |
| Sep | 72,461 cfs | 60,950 cfs | 19,150 cfs | 304,500 cfs |
| Oct | 76,659 cfs | 61,500 cfs | 21,500 cfs | 325,000 cfs |
| Nov | 80,284 cfs | 66,650 cfs | 23,050 cfs | 248,000 cfs |
| Dec | 74,060 cfs | 61,900 cfs | 25,100 cfs | 264,000 cfs |
Monthly averages of daily flow over the gauge's record. Lowest and highest are the extreme monthly averages for that month.
How Mississippi River at Grafton, IL compares in Illinois
- Mississippi River at Grafton, IL ranks #5 of 189 gauges in Illinois in this dataset by average flow.
- That places it in the top 3% in Illinois by average flow.
- The median average flow of gauges in Illinois is 99.5 cfs.
- Among all 2,293 gauges in the dataset, Mississippi River at Grafton, IL ranks #7 by average flow.
Data: U.S. Geological Survey (USGS) (public domain, U.S. federal data).· Updated 2026-11-02 · Text generated from the data and checked against it.
Live values are provisional USGS data. Measurements only, not a safety assessment — for flood warnings see the National Weather Service. Official page: USGS 05587450.