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Weather in Big Sky, Montana for September 2026

Your guide to Big Sky weather in September - trends and predictions

    Snow Forecast ❄️

  • Snowfall in Big Sky during September is quite rare, with fewer than 2 snowy days on average.
    According to Big Sky snow forecast for September 2026, 1 snowy day is expected until the end of the month at Monday, September 28.

    • Temperatures

  • Until now, September 2026 in Big Sky is slightly cooler than the historical average by 0.8 °F.

  • The forecast for the upcoming days in Big Sky predicts a temperature of 16.2 °F, which is slightly above the historical average.

  • In general, the average temperature in Big Sky at the beginning of September is 18.6 °F. As the month progressed, temperatures tended to significantly cool down, reaching an average of 15 °F by the end of September.

    • Rain 🌧️

  • Big Sky experiences moderate rainfall in September, with an average of 7 rainy days and a total precipitation of 201.1 mm.

    • More

  • New! Chat with our AI weatherman - it’s amazing and free.

Average dry days
22
Dry days
Average rainy days
7
Rainy days
Average snowy days
1
Snow days
Average temperatures
17°/9°
Temperatures
Average wind speed
12 km/h
Avg max wind
Average humidity
51 %
Avg humidity

Big Sky Weather September

Move between months or click on a day
August
October
Sun.Mon.Tue.Wed.Thu.Fri.Sat.
1
Partly cloudy
19°
2
Sunny
20°
3
Sunny
19°
4
Sunny
18°
5
Partly cloudy
17°
6
Sunny
20°
7
Thundery outbreaks possible
17°
8
Partly cloudy
16°
9
Light rain shower
17°
10
Thundery outbreaks possible
20°
11
Overcast
16°
12
Moderate or heavy rain with thunder
16°
13
Light rain shower
14°
14
Thundery outbreaks possible
12°
15
Moderate or heavy rain with thunder
12°
16
Moderate or heavy rain with thunder
14°
17
Mist
15°
18
Sunny
17°
19
Overcast
13°
20
Overcast
11°
21
Sunny
18°
22
Overcast
18°
23
Sunny
18°
24
Sunny
19°
25
Overcast
19°
26
Overcast
15°
27
Overcast
17°
28
Patchy rain possible
12°
29
Patchy rain possible
10°
30
Sunny
13°

Temperatures trend during September in Big Sky

See the weather trend as well as the moving average line

September weather in Big Sky day by day

Click on a date for more information
August October
Date Weather Temperatures Rain Snow More
Sept. 1 Partly cloudy
Partly cloudy
 19° /9° 0.5 mm 0 cm
Sept. 2 Sunny
Sunny
 20° /8° 0 mm 0 cm
Sept. 3 Sunny
Sunny
 19° /8° 0 mm 0 cm
Sept. 4 Sunny
Sunny
 18° /7° 0 mm 0 cm
Sept. 5 Partly cloudy
Partly cloudy
 17° /5° 0 mm 0 cm
Sept. 6 Sunny
Sunny
 20° /6° 0 mm 0 cm
Sept. 7 Thundery outbreaks possible
Thundery outbreaks possible
 17° /6° 1.5 mm 0 cm
Sept. 8 Partly cloudy
Partly cloudy
 16° /5° 0 mm 0 cm
Sept. 9 Light rain shower
Light rain shower
 17° /7° 3.2 mm 0 cm
Sept. 10 Thundery outbreaks possible
Thundery outbreaks possible
 20° /7° 0 mm 0 cm
Sept. 11 Overcast
Overcast
 16° /7° 0.6 mm 0 cm
Sept. 12 Moderate or heavy rain with thunder
Moderate or heavy rain with thunder
 16° /5° 6.7 mm 0 cm
Sept. 13 Light rain shower
Light rain shower
 14° /5° 18.1 mm 0 cm
Sept. 14 Thundery outbreaks possible
Thundery outbreaks possible
 12° /3° 3.4 mm 0.5 cm
Sept. 15 Moderate or heavy rain with thunder
Moderate or heavy rain with thunder
 12° /2° 9.6 mm 0 cm
Sept. 16 Moderate or heavy rain with thunder
Moderate or heavy rain with thunder
 14° /3° 11.8 mm 0 cm
Sept. 17 Mist
Mist
 15° /5° 0.6 mm 0 cm
Sept. 18 Sunny
Sunny
 17° /5° 3.2 mm 0 cm
Sept. 19 Overcast
Overcast
 13° /6° 3.7 mm 0 cm
Sept. 20 Overcast
Overcast
 11° /3° 0.4 mm 0 cm
Sept. 21 Sunny
Sunny
 18° /2° 0 mm 0 cm
Sept. 22 Overcast
Overcast
 18° /4° 0.6 mm 0 cm
Sept. 23 Sunny
Sunny
 18° /4° 0 mm 0 cm
Sept. 24 Sunny
Sunny
 19° /5° 0 mm 0 cm
Sept. 25 Overcast
Overcast
 19° /5° 0 mm 0 cm
Sept. 26 Overcast
Overcast
 15° /2° 0 mm 0 cm
Sept. 27 Overcast
Overcast
 17° /4° 0 mm 0 cm
Sept. 28 Patchy rain possible
Patchy rain possible
 12° /3° 1.4 mm 0.3 cm
Sept. 29 Patchy rain possible
Patchy rain possible
 10° /0° 0.9 mm 0 cm
Sept. 30 Sunny
Sunny
 13° /-3° 0.2 mm 0 cm
Next
Important Notice
Our weather forecast for Big Sky in September is based on the analysis of historical data rather than real-time forecast models. While this provides a general overview, weather conditions can change. We recommend that you check the Big Sky forecast closer to your planned date for the most up-to-date weather information.
Change Month
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Big Sky in September - FAQ

What are the expected maximum and minimum temperatures in Big Sky during September?
Enjoy moderate daytime temperatures of up to 17° and cooler nights around 9°. Ideal for a range of outdoor activities, from hiking to city tours.

How much rainfall should be expected in Big Sky during September?
Significant rainfall exceeding 201.1 mm is expected in Big Sky during September, occurring over more than 7 days. Preparing for wet conditions is recommended in your planning.

Will it snow in Big Sky in September 2026?
Big Sky typically sees 3.3 cm of snowfall during September.

What are the typical wind conditions in Big Sky during September?
The average wind speed in Big Sky during September is 12 km/h, suggesting breezy to windy conditions, depending on your activities.

Big Sky snow forecast September 2026

Track daily snowfall levels and discover Big Sky’s snowy potential this September ❄️
On average, Big Sky sees 1 snowy days during September, with approximately 3.3 cm of total snowfall.

September rainfall patterns in Big Sky

Explore the daily rainfall trends and prepare for Big Skys September weather 💧
Typically, Big Sky has 7 rainy days in September with a total of 201.1 mm of rainfall.

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Location coordinates Where is Big Sky?

Get accurate weather forecasts for Big Sky, located at latitude 45.285 and longitude -111.368. Stay updated with localized weather information tailored for Big Sky.

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