Last updated: February 24, 2025
In September, the charming town of West Yellowstone, United States, experiences a delightful transition into autumn. With maximum temperatures reaching a pleasant 28°C (82°F) and an average of 9°C (49°F), mild days compliment cooler nights that can dip to a brisk -8°C (18°F). Rainfall is modest, with 50 mm (2.0 in) spread over just 6 days of the month, creating a refreshing ambiance amidst a humidity level of 67%. Elevate your visit with this incredible blend of warmth and coolness, coupled with scenic beauty that is especially captivating in the fall.
In September, West Yellowstone begins to transition into autumn, offering a pleasant respite from the summer heat. Minimum temperatures dip to a chilly -8°C (18°F), while the average settles at a crisp 9°C (49°F), signaling the approach of colder months. Despite this cooling trend, daytime maximums can still reach as high as 28°C (82°F), allowing for lingering warmth and opportunities to enjoy the stunning natural scenery. This month showcases a delightful balance, where visitors can experience the tail end of summer while preparing for the vibrant colors and chilly nights of fall, making it a fantastic time to explore the area's wonders.
As summer fades into autumn, September in West Yellowstone brings a moderate precipitation total of 50 mm (2.0 in), occurring over just 6 days. This marks a noticeable increase from the drier months of July and August, which collectively recorded only 29 mm (1.2 in) and 36 mm (1.4 in) respectively. Compared to the heavier spring rainfall, September’s precipitation is both beneficial and balanced, contributing to the picturesque landscapes often favored by nature enthusiasts. Heading into October, rainfall slightly rises again to 56 mm (2.2 in), continuing the trend of transitioning weather patterns as the region prepares for the colder, wetter months ahead. Overall, September serves as a bridge, gently easing the burst of summer into the more temperate fall season.
As September arrives in West Yellowstone, the humidity begins to dip, reflecting a gradual shift from the peak summer conditions. Starting at 67%, this month's humidity marks a notable decrease from the 69% experienced in August, continuing the downward trend observed since the onset of summer. Throughout the year, humidity levels start high in winter with 93% in January and gradually decline to this year's lowest point in July, when it reaches 74%. Following September, humidity climbs again with the approach of fall, peaking once more in late autumn and winter. This pattern illustrates the city's distinct seasonal rhythm, capturing the interplay between warmth and moisture as the year progresses.
As summer fades into autumn, September in West Yellowstone, United States, sees a UV Index of 9, indicating a very high exposure category reminiscent of the intense summer months. While the peak values of 11 in May through August signal extreme caution for sun exposure, September maintains a notable level of intensity with a burn time of just 15 minutes. This trend suggests that while the days are getting shorter and cooler, safeguarding against UV radiation remains critical. As we transition into October, the UV Index drops to 6, reflecting the seasonal shift. For comprehensive insights on the UV Index throughout the year, visit West Yellowstone UV Index.
UV Risk Categories
As summer gently transitions into fall, September in West Yellowstone continues to bask in the warmth of sunshine, boasting an impressive 293 hours of bright daylight. This month marks a notable decline from the peak of July, which enjoyed a radiant 396 hours, but it still outshines the earlier months of the year. Notably, September's sunshine is a reminder of the vibrant warmth that lingers after summer, significantly more than the mere 131 hours seen in January. As the year progresses into the cooler months, with October bringing a drop to 250 hours, September stands out as a golden opportunity to soak in the last rays of summer before autumn fully descends.
As September rolls in, West Yellowstone experiences a delightful shift in weather, boasting a significant 74% chance of sunny days. This marks a continuation of the trend seen in the summer months, where sunshine reigns supreme, particularly in June and July. After peaking in the mid-summer, the sunny disposition remains strong into September, indicating that visitors can expect mild temperatures and vibrant landscapes perfect for exploring the natural beauty of the area. While the chances of sun begin to decline in October, September stands out as a prime time for outdoor adventures, aligning beautifully with the rich hues of early fall.
As summer transitions into fall, September in West Yellowstone brings a gentle reduction in daylight, offering about 12 hours of sunlight. This marks a shift from the peak of 15 hours during the height of summer in June and July. The daylight hours begin to wane, echoing the seasonal rhythm as nature prepares for the cooler months ahead. Despite this decrease, September still provides a rich tapestry of light, inviting visitors to enjoy the stunning vistas and vibrant autumn foliage before the days shorten further in October. The gradual decline in daylight from the lush, long summer days signifies not just a change in time but an enchanting transition perfectly suited for exploration and reflection.
As autumn begins to unfurl its splendor in West Yellowstone, September wind whispers gently through the trees at an average speed of 2.6 m/s (6 mph). This month marks a slight uptick from the summer lull, showing a subtle revival of breezy conditions as the region transitions from the warmth of August into the cooler embrace of fall. Interestingly, September's wind speed aligns with those of both April and June, suggesting a regularity in the changing seasons. As the year progresses towards winter, we notice a gradual increase leading up to December's brisk 3.6 m/s (8 mph) winds, hinting at the impending chill. This pattern offers a refreshing reminder of nature's rhythms, inviting visitors to enjoy the tranquil yet invigorating atmosphere that September brings to this stunning part of the United States.
The weather in West Yellowstone changes throughout the year, offering a unique experience in each season. Below is a month-by-month comparison of September's weather with other months, highlighting differences in temperature, precipitation, and other key factors. Click on each section to discover seasonal trends in West Yellowstone and find detailed weather information for every month.
September and January exhibit striking contrasts in weather. September experiences a broader temperature range, with minimums at -8°C (18°F) and maximums reaching a warm 28°C (82°F), offering an average temperature of 9°C (49°F). The month is relatively moderate, with 50 mm (2.0 in) of precipitation over about 6 days and humidity levels around 67%. In stark contrast, January is much colder, featuring minimum temperatures dropping to -28°C (-17°F) and a maximum of just 2°C (36°F), leading to a much chillier average of -9°C (15°F). Precipitation increases slightly to 54 mm (2.1 in) over 12 days, accompanied by higher humidity at 93%, making January feel particularly damp and frigid. For more detailed insights, you can check West Yellowstone weather in January.
September and February present starkly contrasting weather conditions. In September, temperatures range from a chilly -8°C (18°F) at night to a pleasant max of 28°C (82°F), with an average of 9°C (49°F). Precipitation is moderate, totaling 50 mm (2.0 in) over about 6 days, accompanied by a relatively comfortable humidity level of 67%. In contrast, February is much colder, with temperatures dipping as low as -28°C (-19°F) and averaging -9°C (16°F), peaking at just 5°C (41°F). The month sees significantly more precipitation at 96 mm (3.8 in) stretched across 18 days, and humidity levels rise to a high 92%. For a more detailed insight into February weather, you can visit West Yellowstone weather in February.
When comparing the weather in September and March, it's clear that these months represent different seasons and temperature dynamics. September typically experiences a much milder range, with minimum temperatures around -8°C (18°F) and average highs reaching up to 28°C (82°F). In contrast, March is significantly colder, with minimum temperatures plummeting to -29°C (-19°F) and an average temperature of -4°C (26°F).
Precipitation patterns also differ: September sees about 50 mm (2.0 in) across 6 days, while March experiences slightly more precipitation at 63 mm (2.5 in) over 13 days, indicating a wetter month overall. Additionally, humidity levels are higher in March at 89%, compared to September's 67%. For more details on March's weather specifically, you can check West Yellowstone weather in March.
When comparing the weather in September and April, significant differences in temperature and precipitation are evident. September generally offers a more moderate climate, with temperatures ranging from a minimum of -8°C (18°F) to a maximum of 28°C (82°F) and an average of 9°C (49°F). In contrast, April experiences colder conditions, with minimum temperatures plummeting to -19°C (-2°F) and a max of 14°C (57°F), averaging around -1°C (31°F). Additionally, September has less precipitation, totaling 50 mm (2.0 in) over about 6 days, while April sees 72 mm (2.9 in) spread across 15 days, making it a wetter month overall. The humidity is also higher in April at 83%, compared to September's 67%. For more detailed insights, you can check out West Yellowstone weather in April.
When comparing the weather in September and May, September tends to be warmer, featuring average temperatures ranging from a chilly 9°C (49°F) to a maximum of 28°C (82°F). In contrast, May is cooler, with averages between -12°C (11°F) and a maximum of 22°C (71°F). While September experiences moderate precipitation of 50 mm (2.0 in) over six days, May is slightly wetter with 67 mm (2.6 in) of rainfall spread across 13 days. Additionally, humidity is higher in May at 79%, compared to September's 67%. For more detailed insights, check West Yellowstone weather in May.
In comparing the weather between September and June, September tends to be slightly warmer overall, with an average temperature of 9°C (49°F), peaking at 28°C (82°F). In contrast, June averages 11°C (51°F) with a maximum of 27°C (80°F). Precipitation levels are also notable; September sees about 50 mm (2.0 in) of rain over 6 days, while June experiences more rainfall at 67 mm (2.7 in) over 13 days. Humidity is higher in June at 76%, compared to September's 67%. For more detailed insights, check out West Yellowstone weather in June.
When comparing the weather in September and July, it's clear that September experiences a broader temperature range, with minimums dipping to -8°C (18°F) and maximums reaching 28°C (82°F), while July sees milder lows of -2°C (30°F) and highs peaking at 30°C (86°F). The average temperature in September is 9°C (49°F), significantly cooler than July's average of 16°C (61°F). Additionally, September has higher precipitation at 50 mm (2.0 in) over 6 days compared to July's 29 mm (1.2 in) spread over 7 days. Humidity levels also fluctuate slightly, with September at 67% and July a bit higher at 74%. For more detailed insights on July weather, check out West Yellowstone weather in July.
In September, the weather in West Yellowstone showcases a broader temperature range, with minimums dropping to -8°C (18°F) and maximums reaching 28°C (82°F), leading to an average of 9°C (49°F). In contrast, August offers slightly warmer conditions, with temperatures ranging from a minimum of -1°C (30°F) to a maximum of 30°C (87°F), and an average temperature of 14°C (58°F). Precipitation in September is a bit higher, totaling 50 mm (2.0 in) over 6 days, compared to August's 36 mm (1.4 in) over 8 days. Humidity levels are quite similar, with September at 67% and August at 69%. For more details, check out the West Yellowstone weather in August.
In September, temperatures in West Yellowstone range from a minimum of -8°C (18°F) to a maximum of 28°C (82°F), with an average of 9°C (49°F). The month typically sees around 50 mm of precipitation over 6 days, accompanied by a humidity level of 67%. In contrast, October experiences a significant drop in temperatures, with lows plummeting to -32°C (-25°F) and a maximum of only 19°C (66°F), resulting in an average of 0°C (32°F). Precipitation slightly increases to 56 mm over 11 days, and humidity rises to 72%. This stark shift in weather reflects the transition into deeper autumn, making West Yellowstone weather in October quite distinct from September's milder conditions.
In September, the weather is notably milder, with temperatures ranging from a minimum of -8°C (18°F) to a maximum of 28°C (82°F), creating an average of 9°C (49°F). The month sees relatively low precipitation, with about 50 mm (2.0 in) over approximately 6 days, accompanied by a humidity level of 67%. In stark contrast, November brings much colder conditions, with temperatures dipping to a minimum of -24°C (-12°F) and an average of -6°C (22°F), peaking at only 12°C (54°F). This month experiences higher precipitation as well, totaling 62 mm (2.4 in) across 12 days and a significant increase in humidity at 89%. For a detailed look at the weather conditions in November, check out West Yellowstone weather in November.
September and December offer starkly contrasting weather conditions. In September, temperatures vary significantly, with a minimum of -8°C (18°F) and a maximum reaching 28°C (82°F), leading to a pleasant average of 9°C (49°F). The month experiences relatively low precipitation, totaling 50 mm (2.0 in) over just 6 days, along with a comfortable humidity level of 67%. In contrast, December sees a dramatic drop in temperatures, with a chilling minimum of -29°C (-20°F), and an average of -9°C (15°F), peaking at only 5°C (42°F). Precipitation increases to 59 mm (2.3 in), spread out across 14 days, and humidity soars to 94%, creating a much colder and damp environment. For a detailed look at December weather in West Yellowstone, check out West Yellowstone weather in December.
As September arrives in West Yellowstone, the transition from summer warmth to autumn chill becomes palpable. Temperatures begin to dip, with a noticeable shift in the weather that highlights the beauty of the changing seasons. While daytime highs can still reach pleasant levels, the cool nights remind visitors that winter is approaching. Unlike the drier summer months, September sees a slight increase in precipitation, allowing the landscape to flourish in vibrant fall colors, though rain is limited to just a handful of days. This unique blend of crisp air and lingering warmth, combined with moderate humidity, creates a perfect atmosphere for outdoor adventures. For a deeper insight into the local climate patterns, check out our detailed page on West Yellowstone Climate.