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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.

    • Temperatures

  • In general, the average temperature in Big Sky at the beginning of September is 20.1 °F. As the month progressed, temperatures tended to noticeably cool down, reaching an average of 17.9 °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
22°
2
Sunny
23°
3
Sunny
22°
4
Sunny
19°
5
Partly cloudy
15°
6
Sunny
20°
7
Thundery outbreaks possible
20°
8
Partly cloudy
18°
9
Light rain shower
19°
10
Thundery outbreaks possible
19°
11
Overcast
18°
12
Moderate or heavy rain with thunder
15°
13
Light rain shower
10°
14
Thundery outbreaks possible
16°
15
Moderate or heavy rain with thunder
10°
16
Moderate or heavy rain with thunder
9°
17
Mist
14°
18
Sunny
18°
19
Overcast
18°
20
Sunny
19°
21
Light rain shower
16°
22
Moderate or heavy snow with thunder
9°
23
Sunny
17°
24
Sunny
20°
25
Sunny
21°
26
Partly cloudy
16°
27
Sunny
19°
28
Cloudy
19°
29
Thundery outbreaks possible
17°
30
Moderate rain at times
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
 22° /13° 0 mm 0 cm
Sept. 2 Sunny
Sunny
 23° /14° 0 mm 0 cm
Sept. 3 Sunny
Sunny
 22° /14° 0 mm 0 cm
Sept. 4 Sunny
Sunny
 19° /10° 0 mm 0 cm
Sept. 5 Partly cloudy
Partly cloudy
 15° /5° 0 mm 0 cm
Sept. 6 Sunny
Sunny
 20° /7° 0 mm 0 cm
Sept. 7 Thundery outbreaks possible
Thundery outbreaks possible
 20° /10° 0 mm 0 cm
Sept. 8 Partly cloudy
Partly cloudy
 18° /10° 0 mm 0 cm
Sept. 9 Light rain shower
Light rain shower
 19° /13° 6.5 mm 0 cm
Sept. 10 Thundery outbreaks possible
Thundery outbreaks possible
 19° /11° 0 mm 0 cm
Sept. 11 Overcast
Overcast
 18° /11° 0 mm 0 cm
Sept. 12 Moderate or heavy rain with thunder
Moderate or heavy rain with thunder
 15° /8° 13.3 mm 0 cm
Sept. 13 Light rain shower
Light rain shower
 10° /7° 36.3 mm 0 cm
Sept. 14 Thundery outbreaks possible
Thundery outbreaks possible
 16° /8° 0 mm 0 cm
Sept. 15 Moderate or heavy rain with thunder
Moderate or heavy rain with thunder
 10° /5° 19.3 mm 0 cm
Sept. 16 Moderate or heavy rain with thunder
Moderate or heavy rain with thunder
 9° /6° 23.5 mm 0 cm
Sept. 17 Mist
Mist
 14° /6° 0 mm 0 cm
Sept. 18 Sunny
Sunny
 18° /6° 0 mm 0 cm
Sept. 19 Overcast
Overcast
 18° /9° 0 mm 0 cm
Sept. 20 Sunny
Sunny
 19° /11° 0 mm 0 cm
Sept. 21 Light rain shower
Light rain shower
 16° /9° 47.8 mm 0 cm
Sept. 22 Moderate or heavy snow with thunder
Moderate or heavy snow with thunder
 9° /3° 50.8 mm 3.3 cm
Sept. 23 Sunny
Sunny
 17° /4° 0 mm 0 cm
Sept. 24 Sunny
Sunny
 20° /8° 0 mm 0 cm
Sept. 25 Sunny
Sunny
 21° /10° 0 mm 0 cm
Sept. 26 Partly cloudy
Partly cloudy
 16° /10° 0 mm 0 cm
Sept. 27 Sunny
Sunny
 19° /7° 0 mm 0 cm
Sept. 28 Cloudy
Cloudy
 19° /10° 0 mm 0 cm
Sept. 29 Thundery outbreaks possible
Thundery outbreaks possible
 17° /10° 0 mm 0 cm
Sept. 30 Moderate rain at times
Moderate rain at times
 13° /8° 3.6 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 3.32 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.

UV exposure in Big Sky during September

Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️

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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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