Lewis and Clark County (Helena)
September
Weather in Lewis and Clark County, Montana for September 2026
Your guide to Lewis and Clark County weather in September - trends and predictions
In general, the average temperature in Lewis and Clark County at the beginning of September is 25.1 °F. As the month progressed, temperatures tended to moderately fall, reaching an average of 23.9 °F by the end of September.
With an average of 3 rainy days, Lewis and Clark County experiences minimal rainfall in September.
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Temperatures
Rain 🌧️
More
27
Dry days
3
Rainy days
0
Snow days
23°/9°
Temperatures
12 km/h
Avg max wind
48 %
Avg humidity
Lewis and Clark County Weather September
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Temperatures trend during September in Lewis and Clark County
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September weather in Lewis and Clark County day by day
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| Date | Weather | Temperatures | Rain | UV | More |
|---|---|---|---|---|---|
| Sept. 1 |  Sunny | 29° /14° | 0 mm | 7 | |
| Sept. 2 | Sunny | 30° /14° | 0 mm | 8 | |
| Sept. 3 | Sunny | 28° /11° | 0 mm | 7 | |
| Sept. 4 |  Partly cloudy | 20° /9° | 0 mm | 6 | |
| Sept. 5 | Sunny | 19° /4° | 0 mm | 5 | |
| Sept. 6 | Sunny | 23° /5° | 0 mm | 6 | |
| Sept. 7 |  Thundery outbreaks possible | 27° /11° | 0 mm | 6 | |
| Sept. 8 | Sunny | 24° /10° | 0 mm | 6 | |
| Sept. 9 | Thundery outbreaks possible | 24° /10° | 0 mm | 5 | |
| Sept. 10 | Thundery outbreaks possible | 26° /13° | 0 mm | 6 | |
| Sept. 11 |  Overcast | 25° /12° | 0 mm | 6 | |
| Sept. 12 | Thundery outbreaks possible | 20° /7° | 0 mm | 5 | |
| Sept. 13 | Overcast | 21° /8° | 0 mm | 5 | |
| Sept. 14 | Partly cloudy | 24° /8° | 0 mm | 6 | |
| Sept. 15 | Overcast | 15° /10° | 0 mm | 4 | |
| Sept. 16 |  Cloudy | 20° /9° | 0 mm | 5 | |
| Sept. 17 | Sunny | 22° /8° | 0 mm | 6 | |
| Sept. 18 | Sunny | 24° /8° | 0 mm | 6 | |
| Sept. 19 | Overcast | 23° /10° | 0 mm | 5 | |
| Sept. 20 | Sunny | 27° /10° | 0 mm | 7 | |
| Sept. 21 | Overcast | 23° /9° | 20.9 mm | 5 | |
| Sept. 22 | Overcast | 17° /7° | 15.3 mm | 4 | |
| Sept. 23 | Sunny | 24° /4° | 0 mm | 6 | |
| Sept. 24 | Sunny | 26° /6° | 0 mm | 7 | |
| Sept. 25 | Sunny | 27° /10° | 0 mm | 7 | |
| Sept. 26 | Sunny | 19° /8° | 0 mm | 5 | |
| Sept. 27 | Sunny | 24° /5° | 0 mm | 6 | |
| Sept. 28 | Sunny | 25° /7° | 0 mm | 7 | |
| Sept. 29 | Overcast | 26° /9° | 3.6 mm | 6 | |
| Sept. 30 | Cloudy | 20° /10° | 0 mm | 5 | |
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Important Notice
Our weather forecast for Lewis and Clark County 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 Lewis and Clark County forecast closer to your planned date for the most up-to-date weather information.
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Lewis and Clark County in September - FAQ
What are the expected maximum and minimum temperatures in Lewis and Clark County during September?
Enjoy moderate daytime temperatures of up to 23° and cooler nights around 9°. Ideal for a range of outdoor activities, from hiking to city tours.
How much rainfall should be expected in Lewis and Clark County during September?
In September, Lewis and Clark County can expect light to moderate rainfall, totaling 39.8 mm across approximately 3 days. Occasional showers are possible, and planning ahead for them could be helpful.
What are the typical wind conditions in Lewis and Clark County during September?
The average wind speed in Lewis and Clark County during September is 12 km/h, suggesting breezy to windy conditions, depending on your activities.
September rainfall patterns in Lewis and Clark County
Explore the daily rainfall trends and prepare for Lewis and Clark Countys September weather 💧
Typically, Lewis and Clark County has 3 rainy days in September with a total of 39.8 mm of rainfall.
UV exposure in Lewis and Clark County during September
Stay informed about UV levels for safe outdoor activities throughout the month of September ☀️
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Where is Lewis and Clark County?Get accurate weather forecasts for Lewis and Clark County, located at latitude 46.593 and longitude -112.036. Stay updated with localized weather information tailored for Lewis and Clark County.
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