Montana · Big Sky, MT

Gallatin River float season

Gauge 06043500 on the Gallatin Canyon, Big Sky through House Rock and the Mad Mile. Roadside whitewater in a tight forested canyon below Big Sky, where House Rock and the Mad Mile keep rafters coming back.

raftkayak Fullest: May–Jul Leanest: Jan–Mar
Gallatin River — typical flow through the year Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 300 1.5k 3k 5k
median flow for the date middle half of years (25th–75th percentile) most years (10th–90th)

Right now at this gauge

loading CFS

Checking the live gauge…

Live reading from the USGS gauge page for Gallatin River. Provisional data — subject to revision.

The year on this river

In a typical year at the Big Sky gauge, the Gallatin River runs fullest May–Jul and leanest Jan–Mar. Where today's reading falls inside that rhythm matters more than the raw number — the same flow that feels thin in spring can be the summer norm. Half of all past June days at this gauge ran above 2,790 CFS; the February median is 293 CFS.

Median of daily flows in each month across this gauge's full record — half of past days ran above these figures, half below.
Month Typical flow (CFS)
January 296
February 293
March 297
April 433
May 1,670
June 2,790
July 1,070
August 560
September 462
October 432
November 372
December 304

Record context

This gauge has measured daily flow since 1889 — 137 years of record. The largest daily average ever logged here was 8,970 CFS, in June 1974. Rivers do that sometimes; it's why the safety panel above isn't decoration.

Planning dates? The trip-window checker shows what flows have historically looked like on any week you pick for this river, or see what a CFS actually looks like.

More Montana float rivers

Common questions

When is the Gallatin River usually at its fullest?

At the Big Sky gauge, the fullest stretch of a typical year is May–Jul, with the single highest monthly median in June (about 2,790 CFS). The leanest months are usually Jan–Mar.

What is a typical summer flow on the Gallatin River?

The July median at this gauge is about 1,070 CFS — half of past Julys ran higher, half lower. Check the ribbon chart above to see how summer compares with the rest of the year here.

Is the Gallatin River safe to float right now?

No flow number can answer that, and this site never labels a river safe. What the data can tell you is how today's reading compares with 96 years of this date's history — well above typical means pushier, colder, faster water. Pair that context with a PFD, a look at the river from the bank, and a call to a local outfitter before you commit.

Which USGS gauge does this page use?

USGS gauge 06043500 (Gallatin River near Gallatin Gateway, MT), chosen because it best represents the Gallatin Canyon, Big Sky through House Rock and the Mad Mile. Daily records here reach back to 1889.

Data: USGS gauge 06043500, approved daily records 1889–2026, retrieved 2026-08-07. Live readings are provisional and subject to revision. U.S. Geological Survey data is public domain.