Blackfoot River level at Bonner
Montana · Tubing & floating
Measured at USGS 12340000 — Blackfoot River near Bonner MT · NWS forecast point BONM8
Reading taken · as of 58 min ago
Right around its normal summer float level
At 613 CFS, this gauge is inside the middle half of the 93 years USGS has recorded for this date (1898–2026), at 100% of the 610 CFS median.
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Flood stages at Bonner
National Weather Service categories for gauge BONM8, WFO MSO. Impact wording is the NWS's own, verbatim.
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Major flood 17.0 ft
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Moderate flood 16.0 ft
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Minor flood 10.0 ft
- 10.0 ft Flooding to low lying areas adjacent to the river is possible.
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Action 9.5 ft
- Right now 2.13 ft
NWS forecast: 2.13 ft by .
Flow history at Bonner
Daily values from USGS 12340000, updated every 15 to 60 minutes; NWS forecast for BONM8 reissued through the day. Provisional.
Highest crests on record at Bonner
12 on record
| Stage | Flow | Date |
|---|---|---|
| 16.00 ft | — | Feb 9, 1996 |
| 11.65 ft | — | Jun 4, 1953 |
| 11.09 ft | 18,800 CFS | May 11, 2018 |
| 10.89 ft | 19,200 CFS | Jun 10, 1964 |
| 10.74 ft | 18,100 CFS | Jun 20, 1975 |
| 10.50 ft | 16,144 CFS | May 18, 1997 |
| 10.01 ft | 17,000 CFS | Jun 9, 2011 |
| 9.98 ft | 6,500 CFS | Jun 2, 1972 |
| 9.48 ft | 13,140 CFS | Jun 15, 1976 |
| 8.78 ft | 11,290 CFS | May 14, 1971 |
Crests published by the National Weather Service.
About Blackfoot River at Bonner
The daily record at this station opens on 1 July 1898, which makes it one of the oldest series feeding this site. USGS publishes statistics covering about 90 years, and across them the river shows a clean snowmelt signature: a median of 4,470 CFS in May and 4,280 in June against 523 in January, a swing of more than eight to one on a 2,287 square mile basin.
The NWS flood ladder here has an unusual shape. Action stage is 9.5 feet and minor flood is 10, but moderate does not arrive until 16 feet and major at 17. Six feet separate minor from moderate. Only one crest in the historical list has ever reached the moderate rung: 16.0 feet in February 1996.
Blackfoot River at Bonner — common questions
5 questions
When does this river peak?
Late spring. The published medians put May at 4,470 CFS and June at 4,280, with April already at 1,760, while the winter months sit between 523 and 648. That is snowmelt driving the hydrograph, so the useful question about any reading here is where the snowpack is in its cycle, which the percent of normal figure above answers for today's date.
Why is there such a large gap between minor and moderate flood stage?
The NWS has set minor flood at 10 feet and moderate at 16 on this forecast point, a six foot gap that is much wider than typical. The recorded crests suggest why: the list runs 11.65, 11.09, 10.89 and 10.74 feet for the events after 1996, with only the February 1996 crest of 16.0 feet reaching the moderate threshold at all.
Does rain upstream change Blackfoot River at Bonner quickly?
Yes. It is free-flowing, so rain upstream moves it directly. Several feet in a few hours is normal after a heavy storm.
Is Blackfoot River at Bonner high or low for this time of year?
The USGS median flow for late September here is 610 CFS, from 93 years of record (1898–2026). Today sits inside the middle half of those years, at 100% of the median. 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 12340000 every 15 to 60 minutes, and the National Weather Service reissues the flood forecast for BONM8 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.