Gallatin River
The best month to fish the Gallatin River is September. The month to avoid is August. Right now, in September, it is worth going.
- January: 71 out of 100
- February: 71 out of 100
- March: 71 out of 100
- April: 53 out of 100
- May: 58 out of 100
- June: 56 out of 100
- July: 71 out of 100
- August: 48 out of 100
- September: 73 out of 100
- October: 71 out of 100
- November: 71 out of 100
- December: 71 out of 100
GAUGE 06052500 · COLOURED BY SEPTEMBER
Month by month
| MONTH | TYPICAL FLOW | RANGE (P20–P80) | WATER | AIR HIGH | RAIN | SCORE |
|---|---|---|---|---|---|---|
| January | 629 cfs | 572–689 | — | — | — | 71 |
| February | 623 cfs | 563–686 | — | — | — | 71 |
| March | 760 cfs | 621–834 | — | — | — | 71 |
| April | 1,070 cfs | 946–1,213 | 46.7°F | — | — | 53 |
| May | 2,363 cfs | 1,758–2,858 | 51.4°F | — | — | 58 |
| June | 2,999 cfs | 2,073–4,044 | 56.6°F | — | — | 56 |
| July | 750 cfs | 401–1,065 | 67.2°F | — | — | 71 |
| August | 373 cfs | 290–485 | 64.7°F | — | — | 48 |
| SeptemberNOW | 457 cfs | 369–554 | 56.9°F | — | — | 73 |
| October | 678 cfs | 626–794 | — | — | — | 71 |
| November | 791 cfs | 725–890 | — | — | — | 71 |
| December | 648 cfs | 619–738 | — | — | — | 71 |
WHERE THESE NUMBERS COME FROM
Flow and water temperature are medians of the monthly means reported by USGS gauge 06052500 over 2006-2025. Air temperature and precipitation are ten-year normals from Open-Meteo at this river’s gauge coordinates.
The window is deliberate. USGS’s own full-record statistics for a dammed river reach back before the dam — at Lees Ferry, to 1922, forty-one years before Glen Canyon closed — and describe a river that no longer exists.
Flow is scored against this river’s own fishable band of 629–791 cfs. There is no universal band: 8,000 cfs is low water on a big tailwater and a flood on a spring creek.
Water temperature is a ceiling rather than a weight. Above about 68°F a trout that is fought and released frequently dies anyway, so no month above that line is scored as worth booking, however good its flow.
Regulations, licences and access change without notice and are not reproduced here as fact — check the state agency before you travel. A median describes twenty years; it does not forecast your week. Source: U.S. Geological Survey, National Water Information System.