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Big Sky in September

Mild and damp, as the days shorten.

Typical weather, averaged over 30 years

September in Big Sky is mild: highs near 68°F, lows near 40°F. Rain falls on about three days a week, and the days shorten by 1 hour 8 minutes from the first week to the last.September in Big Sky is mild: highs near 20°C, lows near 4°C. Rain falls on about three days a week, and the days shorten by 1 hour 8 minutes from the first week to the last.

High
68°F20°Caverage
Low
40°F4°Caverage
Wet days
3a week · 37% of days
Daylight
12h 26mon average

Is September a good time to visit Big Sky?

A good month, just outside Big Sky's best months, which run from July to August.

How we judge it: every month is scored on how close its typical high comes to the range from 70°F to 80°F, how mild its nights are, and how rarely it rains. The best months are the run of months that scores best.How we judge it: every month is scored on how close its typical high comes to the range from 21°C to 27°C, how mild its nights are, and how rarely it rains. The best months are the run of months that scores best.

How September sits in the year

week by week

Temperature

Highs near 68°F in September, against 29°F to 78°F through the year.Highs near 20°C in September, against -2°C to 26°C through the year.

Chance of a wet day

37% of days in September, against 36% to 60% through the year.

Cloud cover

41% cover in September, against 30% to 65% through the year.

Daylight

12h 26m in September, against 8h 48m to 15h 35m through the year.

Week by week, lightly smoothed, with September shaded. The olive line marks the best months. Hover or tap a week for its figures.

Either side

  1. August78°26°low 48°low 9°3 wet days a weekRain on about three days a week.
  2. September68°20°low 40°low 4°3 wet days a weekRain on about three days a week.
  3. October55°13°low 29°low -2°3 wet days a weekRain on about three days a week.

Where Big Sky sits, in September

America/Denver
this place
typical high in September 40°F4°C95°F35°C
Sunrise, mid-September
7:02 AMsets 7:39 PM
Above the sea
2,134 mhigh country
Latitude
45.3°Nnorthern hemisphere
Nearest of ours
Moose176 km south

The land around Big Sky, shaded by its typical high in September, the planning map's own layer. Hover the map for the figure at that spot; tap it on a phone. Clock times are local, for the 15th.

Elsewhere in United States in September

high · low · wet days
See September on the planning mapThe whole year in Big Sky

Typical weather, averaged over 30 years (1995–2024), from the 11 km grid square nearest Big Sky. Temperatures are adjusted against 66 weather stations: daytime highs read about 3.1°F cold in the source data and are raised to match, and both highs and lows are adjusted for the town's height (2,134 m) against the climate model's (2,477 m).Temperatures are adjusted against 66 weather stations: daytime highs read about 1.7°C cold in the source data and are raised to match, and both highs and lows are adjusted for the town's height (2,134 m) against the climate model's (2,477 m). Daylight is calculated from latitude. Charts are lightly smoothed week to week; the figures in the table are not. Source: Copernicus ERA5-Land reanalysis; cloud cover from NASA's MERRA-2 reanalysis, on a coarser grid of about 50 km. Contains modified Copernicus Climate Change Service information 2026; neither the European Commission nor ECMWF is responsible for any use of it. These are averages, not a forecast.

Daylight is calculated from latitude. Charts are lightly smoothed week to week; the figures in the table are not.

Source: Copernicus ERA5-Land reanalysis; cloud cover from NASA's MERRA-2 reanalysis, on a coarser grid of about 50 km. Contains modified Copernicus Climate Change Service information 2026; neither the European Commission nor ECMWF is responsible for any use of it. These are averages, not a forecast.