September & October Weather Forecast for Ennis, Montana
Fall in Ennis, Montana is a season of transition. Crisp mornings, golden cottonwoods along the Madison River, and the first hints of snow make September and October a special time for both locals and visiting anglers. If you’re planning a trip to Ennis this fall, here’s what the weather looks like and how to prepare.
🌡️ Temperature Trends for Fall 2025
September starts out relatively mild, with average highs in the low 70s °F and lows in the upper 30s °F. By October, highs dip into the upper 50s °F and lows commonly reach the upper 20s °F—so pack your layers.
Below is a trend chart of expected average daily highs and lows for September and October in Ennis, MT:
(Chart: Average daily highs in red, lows in blue, with shaded area showing day-to-night range.)
🌨️ Precipitation Outlook
- September: Around 1 inch of precipitation, mostly as rain early in the month. Occasional light snow may appear late in September.
- October: Slightly wetter at 1.1 inches, with precipitation more likely to fall as snow. By mid-to-late October, measurable snow accumulation is common.
National Weather Service Forecast – Ennis, MT
Farmers’ Almanac Long Range Outlook – Montana
❄️ Frost & Snowfall Calendar
Here’s a handy look at when to expect frost, freezes, and snow around Ennis:
| Event | Typical Date Range | 2025 Forecast Date |
|---|---|---|
| First Light Frost | Sept 20 – Sept 30 | Sept 25, 2025 |
| First Hard Freeze | Oct 10 – Oct 20 | Oct 15, 2025 |
| First Likely Snow | Oct 15 – Oct 25 | Oct 20, 2025 |
This means by late September, you’ll want a warm jacket in the mornings. By mid-October, snowpack is possible, and icy conditions may affect travel or river access.
🎣 What This Means for Anglers
For fly fishers visiting Ennis in September and October:
- Early September: Milder days, with active trout feeding before the cold sets in. Great time for terrestrials and nymph rigs.
- Late September: Frosty mornings, excellent streamer season begins as browns get aggressive before spawning.
- October: Be ready for snow, but also for solitude. Cold, crisp days offer some of the best brown trout fishing of the year.
Be prepared for quick-changing weather and remember: layers, waterproof shells, and insulated gear are essential for comfort.
Final Thoughts
Fall in Ennis, MT offers both challenges and rewards. From the first frost to the first real snowfall, the weather sets the stage for an unforgettable Montana fly fishing experience.
👉 Check the National Weather Service daily forecast before your trip, and keep an eye on long-range trends in the Farmers’ Almanac.
🍂 Whether you’re chasing trout or just taking in the fall scenery, September and October are magical months to visit the Madison Valley.
