United States
Yellowstone in September
🍂 AutumnCool and mostly dry.
🎒 Pack: warm jacket for evenings
Why September scores 8.9What goes into the score
How it works- Weather comfort8.6
- !Cool (16°C highs / 1°C lows)
- ✓Comfortable humidity (dew point -0.1°C)
- ✓Mostly dry (~40 mm rain)
- Air quality9.3
- ✓Good (within WHO guideline) (PM2.5 ~9 µg/m³)
- Seasonal hazards10.0
- ·No notable seasonal hazards
- Safety baseline7.5
- ·Increased caution
| Sep | Jul | |
|---|---|---|
| Score | 8.9 Excellent | 9.4 Excellent |
| Season | 🍂 Autumn | ☀️ Summer |
| High / low | 16° / 1° | 22° / 6° |
| Rain | 40 mm | 33 mm |
| Humidity | dew pt 0° | dew pt 6° |
| PM2.5 | 9 µg/m³ | 6 µg/m³ |
Typical-month data: NASA POWER (MERRA-2 reanalysis) 2015–2024 (modelled, not a forecast). Temperatures: Yellowstone Lake weather-station normals. Rainfall: Yellowstone Lake weather-station normals (national met service).
Holidays & crowdsSeptember 2027
Long weekendThere's at least one long weekend. Domestic travel picks up and popular spots get busier over those days.
- Labor Day 4–6 Sep · 3 days off in a row
National holidays only; regional holidays and school breaks aren't included. Source: holidays (open-source public-holiday calendar).
Nature calendarBlossoms, leaves & seasons in Yellowstone
- Snowy daysTypical datesSnow likely Oct–May (most in Jan: ~16 days)
Average number of days with snowfall at Yellowstone Lake. About 91 cm of snow falls in an average Jan.
Source: Yellowstone Lake weather-station normals (national weather service, via Wikipedia climate table)
Explore YellowstoneEvents, sights, food & souvenirs
Check event dates locallyThe first US national park, mainly in Wyoming, known for geysers including Old Faithful, hot springs, a large canyon and wildlife such as bison, elk and wolves.
Summer road seasonDate variesMost roads usually open late April to early November
Most park roads are open to cars only in this window.
Why go: Plan around road openings; summer is very busy.
Where: Park roads
Elk rutDate variesUsually September to October
Bull elk bugle and compete for mates.
Why go: Keep a safe distance from aggressive bulls.
Where: Mammoth Hot Springs and meadows
Coming up later
Winter seasonDate variesUsually mid-December to mid-March
Over-snow vehicle access with steaming geysers.
Why go: Only the north road to Lamar is open to cars.
Where: Interior of the park via snowcoach or snowmobile
Old Faithful
A geyser erupting at fairly predictable intervals in the Upper Geyser Basin.
💡 Eruption predictions are posted at the visitor centre.
Grand Prismatic Spring
The largest hot spring in the US, with bands of colour from microbial mats.
💡 The Fairy Falls trail overlook gives the best aerial view.
Grand Canyon of the Yellowstone
A yellow-walled canyon with the Lower Falls.
Lamar Valley
A valley known for bison herds and wolf watching.
💡 Dawn and dusk are best for wildlife; bring binoculars.
Mammoth Hot Springs
Travertine terraces formed by hot water near the park's north entrance.
Yellowstone Lake
A large high-altitude lake that usually stays frozen until late May or June.
Bison burger
Burgers made from bison meat.
💡 Park lodges and gateway towns
Huckleberry treats
Wild huckleberry in ice cream, jam and pies.
💡 Gateway towns and park shops
Rocky Mountain trout
Trout dishes served in park lodges and gateway-town restaurants.
💡 Lodge restaurants
Huckleberry products
Jams, candy and syrups.
💡 Park and gateway town shops
National park merchandise
Books and maps from the park nonprofit.
💡 Visitor centre stores