Rivermatics

4 USGS Streamgages · Columbia River system

Flathead River flows and levels

Flathead River is gauged at 4 USGS streamgages in Montana, each tracked by Rivermatics. The mainstem runs about 258 miles (415 km) from headwaters to outlet. It drains into the Columbia River system. Drainage area at the gauges ranges from 4,473 square miles at Flathead River at Columbia Falls, MT up to 9,024 at Flathead River at Perma, MT. The gauged reach falls about 510 feet, from 2,989 feet down to 2,479. Rivermatics issues a daily machine-learned 14-day flow outlook at 3 of them.

Gauges on this river, upstream to downstream

Ordered by drainage area, which is how far down the river each gauge sits. April and July figures are long-term median daily flows for that month from the USGS record — historical normals, not a forecast and not today's reading.

USGS streamgages on this river, ordered upstream to downstream
Gauge State Drainage sq mi Elevation ft April p50 cfs July p50 cfs Forecast
Flathead River at Columbia Falls, MT MT 4,473 2,989 10,682 10,764.8 14-day + temp
Flathead River at Foys Bend near Kalispell, MT MT 5,341 2,893 — — —
Flathead River near Polson, MT MT 7,079 2,698 9,233 12,643.9 14-day + temp
Flathead River at Perma, MT MT 9,024 2,479 9,645.3 12,518.7 14-day + temp

Typical flow by month at Flathead River at Perma, MT

The furthest-downstream gauge on this river, so the fullest flow it carries here. Long-term daily discharge percentiles from the USGS record (up to 42 years of data), averaged within each month. These describe the historical normal range — they are not a forecast and not today's reading.

Historical monthly discharge percentiles in cubic feet per second
Month Low p10 Typical p50 High p90 Range
January 6,665.8 9,821 13,571
February 6,145.2 8,855.2 14,437.9
March 4,763.2 8,218.7 13,035.5
April 4,641.3 9,645.3 17,460
May 8,600 15,812.9 32,258.1
June 12,220 22,826.7 44,200
July 6,826.5 12,518.7 22,522.6
August 4,284.8 6,678.1 11,527.7
September 4,187.7 6,322 11,128.7
October 4,474.2 7,532.9 11,606.5
November 5,268.3 9,135.7 12,970
December 7,637.4 10,163.5 13,735.5

All values in cubic feet per second (cfs).

Common questions

When does the Flathead River run highest?
June, on the long-term record at Flathead River at Perma, MT — the furthest-downstream gauge Rivermatics tracks on this river. Median daily flow there is about 22,826.7 cfs that month, against 6,322 cfs in September, the lowest. Upstream gauges peak on their own schedule; the table on this page gives April and July for each.
How many gauges are on the Flathead River?
Rivermatics tracks 4 USGS streamgages on the Flathead River, across Montana. Each has its own page with the site's full flow record and monthly normals. The river may carry other gauges that publish neither daily values nor discharge statistics; those are not tracked here.
Is there a flow forecast for the Flathead River?
Yes, at 3 of the 4 gauges. Rivermatics trains a machine-learned model — a temporal-fusion transformer — on each basin's observed flows, weather and snowpack, and issues a daily outlook reaching 14 days ahead: a median estimate inside a confidence band, not a single number to bet on. Every forecast is scored against days the model never trained on, and that track record is published on each gauge's live screen.
What river system is the Flathead River part of?
The Flathead River drains into the Columbia River system — it is a tributary somewhere in that chain, following the flowpath down to its terminal river. Rivermatics builds this from the USGS/geoconnex reference-mainstem network rather than from names.
Can I use Flathead River data for flood or safety decisions?
No. Rivermatics provides estimates, not guarantees, and the readings and forecasts here may be delayed, inaccurate, or wrong. Do not use them for navigation or for any safety, rescue, or emergency decision. Check the National Weather Service and USGS directly, and use your own judgment.

Other rivers in the Columbia River system

Browse nearby gauges by state