Where the water stands right now against the four official thresholds:
| Flood stage | Level (ft) | What it means |
|---|---|---|
| Major flood stage | 20 | extensive inundation and significant evacuations — a serious event |
| Moderate flood stage | 18 | some buildings and roads inundated; evacuations possible |
| Minor flood stage | 16 | low-lying roads and fields near the river start to flood |
| Action stage | 15 | water is approaching flood level — time to pay attention |
| # | Crest (ft) | Date | vs. minor flood stage |
|---|---|---|---|
| 1 | 21.68 | 1979-03-07 | +5.68 above |
| 2 | 20.6 | 2018-02-23 | +4.6 above |
| 3 | 20.14 | 2008-01-11 | +4.14 above |
| 4 | 19.68 | 1943-05-20 | +3.68 above |
| 5 | 19.02 | 1959-02-13 | +3.02 above |
| 6 | 18.96 | 1982-02-24 | +2.96 above |
| 7 | 18.79 | 2015-07-14 | +2.79 above |
| 8 | 18.7 | 2015-12-31 | +2.7 above |
| 9 | 18.63 | 2005-01-15 | +2.63 above |
| 10 | 18.6 | 1970-05-15 | +2.6 above |
| 11 | 18.3 | 1926-10-06 | +2.3 above |
| 12 | 18.22 | 1991-01-01 | +2.22 above |
Historic crests recorded at this gauge by the National Weather Service — the 12 highest on file.
The marker is this gauge; nearby gauges load live and are clickable.
The live reading at the top of this page answers that: the gauge is compared against its official NWS flood stages every 15 minutes. Minor flooding at this gauge begins at 16 ft. Blue means normal, yellow is action stage, orange minor, red moderate and dark red major flooding.
major flood stage 20 ft, moderate flood stage 18 ft, minor flood stage 16 ft, action stage 15 ft. These are official National Weather Service thresholds set specifically for this gauge, not generic values.
The highest crest on file at this gauge is 21.68 ft, reached on 1979-03-07 — that is 5.68 ft above minor flood stage. The full list of the highest crests is in the table on this page.
From the NOAA National Water Prediction Service, the official U.S. river gauge network — a U.S. government work in the public domain. Live stage is refreshed every 15 minutes; flood thresholds and historic crests are refreshed monthly. For life-safety decisions follow NWS Romeoville and local emergency management.