Henrys Fork level at Island Park
Idaho · Fishing & wading
Measured at USGS 13042500 — HENRYS FORK NR ISLAND PARK ID · NWS forecast point ISLI1
Reading taken · as of 18 min ago
Up and off-colour — heavier water than usual for wading
At 1,160 CFS, this gauge is running 153% of normal for mid-September — above the 756 CFS median USGS has recorded for this date across 93 years of record (1933–2026).
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Flow history at Island Park
Daily values from USGS 13042500, updated every 15 to 60 minutes; NWS forecast for ISLI1 reissued through the day. Provisional.
Highest crests on record at Island Park
12 on record
| Stage | Flow | Date |
|---|---|---|
| 6.15 ft | 2,770 CFS | Apr 26, 1946 |
| 6.06 ft | 3,030 CFS | May 23, 1984 |
| 5.96 ft | 2,580 CFS | Jun 1, 1943 |
| 5.87 ft | 2,560 CFS | Jul 18, 1955 |
| 5.85 ft | 2,580 CFS | Aug 26, 1983 |
| 5.82 ft | 2,700 CFS | May 18, 1982 |
| 5.80 ft | 2,040 CFS | Jul 21, 2015 |
| 5.80 ft | 2,610 CFS | May 13, 1971 |
| 5.80 ft | 2,430 CFS | Jun 9, 1999 |
| 5.45 ft | 1,930 CFS | Jul 30, 2013 |
Crests published by the National Weather Service.
About Henrys Fork at Island Park
In Idaho — the reading paddlers, anglers and outfitters here check before committing to a shuttle. Box Canyon and Last Chance; world-famous dry-fly water.
Henrys Fork at Island Park — common questions
3 questions
What makes the flow change on Henrys Fork at Island Park?
Rain upstream, plus seasonal baseflow. The 12-month chart shows how it behaves through the year.
Is Henrys Fork at Island Park high or low for this time of year?
The USGS median flow for mid-September here is 756 CFS, from 93 years of record (1933–2026). Today is 153% of it. The comparison is what makes the raw number mean anything: the same reading is a drought on one river and a flood on another.
How often does this reading update?
USGS transmits from gauge 13042500 every 15 to 60 minutes, and the National Weather Service reissues the flood forecast for ISLI1 a few times a day — more often when the river is rising. This page refreshes from both when you open it. The timestamp is in the gauge's local time.