Last updated: February 24, 2025
In Sun Valley, United States, September unfolds with warm days and cool nights, showcasing a maximum temperature of 29°C (84°F) and an average of 10°C (51°F). However, as the month progresses, temperatures can dip to a brisk minimum of -13°C (10°F), emphasizing the region's diverse climate. With 30 mm (1.2 in) of precipitation spread over 5 days, the air maintains a comfortable humidity level of 46%, offering a refreshing atmosphere perfect for outdoor activities. Whether you're hiking through scenic trails or relaxing in the crisp evening air, September in Sun Valley provides a delightful blend of warmth and coolness, enticing visitors to explore its stunning natural beauty.
In September, Sun Valley begins its transition into cooler fall weather, with temperatures reflecting a notable shift. The month experiences a minimum temperature of -13°C (10°F) and an average of 10°C (51°F), offering a crisp yet inviting atmosphere. As the days progress, the warmth peaks with a maximum of 29°C (84°F), inviting residents and visitors alike to enjoy the last remnants of summer warmth before autumn sets in. This blend of cooler nights and pleasantly warm days creates an ideal backdrop for outdoor activities, showcasing the region's stunning scenery and vibrant fall foliage. Overall, September balances the end of summer's warmth with the early whispers of winter, making it a captivating month in Sun Valley.
September brings a gentle transition in Sun Valley's climate, with precipitation totaling 30 mm (1.2 in) over the course of approximately 5 days. This marks a mild decrease compared to the previous months, suggesting a gradual shift from the wetter summer season. As the region bids farewell to August's sporadic rain, September often offers clearer skies while still retaining some moisture. This moderate rainfall, combined with an average of less than one inch of precipitation, helps prepare the landscape for the impending autumn foliage, making it an ideal time for both outdoor activities and enjoying the changing seasons. As the year progresses, it’s clear that Sun Valley’s weather pattern reflects a notable rhythm, with early autumn hinting at a shift towards the cooler months ahead.
As the summer wanes into September in Sun Valley, the humidity begins to rise slightly from the lows of August, settling at 46%. This marks a gradual transition from the notably dry conditions of the peak summer months, where July and August recorded their lowest humidities at 53% and 42%, respectively. In contrast to the damp chill of winter, when humidity levels hover around 91% to 92% in January and February, September provides a refreshing balance of crisp air and moderate moisture. The trend showcases a persistent decline in humidity throughout the warmer months, followed by a subtle increase as autumn approaches, hinting at the changing seasons that lie ahead.
As September rolls into Sun Valley, the UV Index remains notably high at 9, categorizing it as very high. This trend showcases the area's consistent exposure to intense sunlight, reminiscent of the peak summer months when the UV Index reached extremes of 11 and 12. The burn time, which is just 15 minutes, reinforces the necessity for effective sun protection, particularly as fall approaches. While the UV levels begin to ease in October, September still demands careful attention to sun safety—so don’t forget your sunscreen! For more detailed information on UV exposure throughout the year, visit Sun Valley UV Index.
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September in Sun Valley welcomes a delightful transition as summer gradually yields to fall, boasting 307 hours of sunshine. This month marks a slight decline from the glorious peak of 402 hours in July, yet it still reflects a significant abundance of daylight, particularly when compared to the 211 hours in November. The days grow shorter and crisp air begins to hint at autumn, enhancing the beauty of the sunlit landscapes. As the golden hues of summer linger, September emerges as a perfect time to enjoy outdoor adventures, while also foreshadowing the waning warmth that will soon give way to the chill of winter. The overall trend showcases a steady surge of sunshine from the depths of winter, culminating in the vibrant energy of summer before gently tapering into the cooler months.
In Sun Valley, September boasts a promising 82% chance of sunny weather, making it one of the sunniest months of the year. This trend reflects a gradual increase in sunshine that begins in the spring, with March and April already showing solid chances at 57% and 56%, respectively. As summer approaches, there’s a noticeable peak with June and July maintaining a robust 78% and 71% chance of clear skies. August continues this sunny spell, but it’s September that truly shines the brightest, marking a delightful transition into fall with ample opportunities to enjoy the outdoors under nearly guaranteed sunshine. This upward surge in sunshine captures Sun Valley's charm, inviting visitors and locals alike to bask in the warm rays before the cooler months take over.
As the summer warmth begins to fade, September in Sun Valley sees a delightful shift in daylight duration, offering approximately 12 hours of light each day. This gradual decline from the sun-drenched stretch of 15 hours in July and June signals the arrival of autumn, where vibrant foliage paints the landscape. The transition from summer's lengthy days to the shortening sunlight hours reflects a rhythmic pattern, where daylight peaks in mid-summer before heading toward the crisp 10 hours typical of October. This cyclical dance not only enhances the beauty of the changing seasons but also invites residents and visitors alike to savor the golden hues of early fall in this picturesque region.
As September arrives in Sun Valley, the winds stir gently, averaging 2.1 m/s (5 mph)—a slight increase from the summer months. This marks a subtle shift in the seasonal breeze, suggesting the transition from the warm embrace of summer to the crispness of autumn. Throughout the year, wind speeds feel relatively consistent, with the highs peaking in early summer and tapering as winter approaches. September’s gentle gusts, mirroring October’s similar pace, invite outdoor enthusiasts to savor the scenic beauty while hinting at the vibrant colors of fall that are just around the corner. The overall trend reflects a manageable breeze, perfect for leisurely hikes or cozy evenings by the fire.
The weather in Sun Valley 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 Sun Valley and find detailed weather information for every month.
The weather in September is significantly milder than in January, with temperatures ranging from a minimum of -13°C (10°F) to a maximum of 29°C (84°F) and an average of 10°C (51°F). In contrast, January experiences much colder conditions, featuring a minimum of -27°C (-16°F), an average of -8°C (17°F), and a maximum of only 2°C (36°F). Additionally, September has lower precipitation at 30 mm (1.2 in) over about 5 days, while January sees higher precipitation levels of 56 mm (2.2 in) spread over 10 days, along with much higher humidity at 91%. For more details about January weather patterns, you can check Sun Valley weather in January.
September and February present contrasting weather conditions. In September, temperatures range from a chilly minimum of -13°C (10°F) to a warm maximum of 29°C (84°F), with an average of 10°C (51°F). The month sees relatively low precipitation, totaling 30 mm (1.2 in) over about 5 days and a comfortable humidity of 46%. In stark contrast, February brings much colder temperatures, with a minimum of -22°C (-8°F) and a maximum of only 6°C (42°F), resulting in an average temperature of -8°C (18°F). This month is marked by significantly higher precipitation at 86 mm (3.4 in) over 13 days and a high humidity level of 92%. For more information on February weather specifically, you can visit Sun Valley weather in February.
In comparing the weather between September and March, significant differences emerge both in temperature and precipitation. September offers a more moderate climate with minimum temperatures around -13°C (10°F), an average of 10°C (51°F), and highs reaching up to 29°C (84°F). It experiences relatively low precipitation at 30 mm (1.2 in) over just 5 days, along with a comfortable humidity level of 46%.
In contrast, March presents a much colder landscape, with minimum temperatures dropping to -22°C (-7°F) and an average of -3°C (26°F). The maximum temperature is only 10°C (50°F). This month has higher precipitation levels at 60 mm (2.4 in) spread over 12 days and a notably elevated humidity of 85%. For a closer look at the specific weather conditions in March, you can check out Sun Valley weather in March.
When comparing the weather in September and April, notable differences emerge. September boasts a more temperate climate with an average temperature of 10°C (51°F), a maximum of 29°C (84°F), and significantly less precipitation at 30 mm (1.2 in) over just 5 days, resulting in a relatively low humidity of 46%. In contrast, April is much cooler, with an average temperature of 0°C (31°F) and a maximum of only 14°C (57°F). Precipitation is higher in April, with 52 mm (2.0 in) spread across 11 days, contributing to a much wetter atmosphere and an elevated humidity level of 76%. For those interested in specifics, you can find more information about Sun Valley weather in April.
In September, the weather tends to be warmer overall, with average temperatures around 10°C (51°F) and a maximum reaching up to 29°C (84°F), compared to May's cooler average of 4°C (40°F) and a maximum of 24°C (75°F). However, May experiences more frequent rainy days, with 61 mm (2.4 in) of precipitation over 13 days, while September sees only 30 mm (1.2 in) across 5 days. Additionally, humidity levels are higher in May at 66%, compared to September's 46%, contributing to a noticeably different feel in the air. For those interested in a detailed look at May weather in Sun Valley, you can find more information here: Sun Valley weather in May.
In comparing the weather conditions of September and June, we can see distinct differences in temperature and precipitation patterns. September experiences a wider temperature range, with minimums dropping to -13°C (10°F) and maximums reaching 29°C (84°F), while June has milder fluctuations, with minimums at -4°C (24°F) and maximums peaking at 28°C (82°F). Precipitation is also notable; September sees 30 mm (1.2 in) over 5 days, whereas June has a higher total of 46 mm (1.8 in) across 9 days. Additionally, June tends to be more humid at 62%, compared to September's 46%. For a more detailed look at June weather, you can visit Sun Valley weather in June.
In comparing the weather of September and July, it is evident that September experiences a wider temperature range, with minimums dropping to -13°C (10°F) and maximums reaching up to 29°C (84°F). The average temperature in September is cooler at 10°C (51°F) compared to July's average of 16°C (62°F). Additionally, September has slightly more precipitation with 30 mm (1.2 in) over 5 days, while July sees less rain at 15 mm (0.6 in) over just 4 days. The humidity in July is also higher at 53%, compared to September's 46%. For a closer look at July’s weather specifics, you can visit Sun Valley weather in July.
September weather in Sun Valley shows a notable shift compared to August. While August boasts a warmer average temperature of 15°C (60°F), September cools down to an average of 10°C (51°F), with the minimum temperature dipping to -13°C (10°F). Despite a similar level of precipitation, September experiences slightly less rainfall at 30 mm (1.2 in) over 5 days, compared to August's 33 mm (1.3 in) over 6 days. Additionally, humidity levels are slightly higher in September at 46% compared to August's 42%. For a more detailed look at what to expect, check out Sun Valley weather in August.
September offers a more temperate experience with average temperatures around 10°C (51°F), peaking at 29°C (84°F), while October sees a significant drop, with averages plummeting to just 2°C (35°F) and a maximum of 22°C (71°F). Precipitation increases slightly in October, totaling 42 mm (1.6 in) over 7 days compared to September’s 30 mm (1.2 in) over 5 days. Additionally, humidity rises from 46% in September to 64% in October, contributing to a cooler and somewhat wetter atmosphere. For more detailed information, visit Sun Valley weather in October.
In September, the weather is generally milder, with temperatures ranging from a minimum of -13°C (10°F) to a maximum of 29°C (84°F) and an average temperature of 10°C (51°F). Precipitation is relatively low at 30 mm (1.2 in), occurring over about 5 days, and humidity is moderate at 46%. In contrast, November brings a more pronounced chill, with temperatures dropping significantly; the minimum reaches -23°C (-10°F) and averages around -4°C (26°F), with a maximum of 12°C (55°F). Along with increased precipitation of 46 mm (1.8 in) over 9 days, the humidity also rises sharply to 83%. For more detailed information on November weather specifics, you can visit Sun Valley weather in November.
In September, temperatures in Sun Valley exhibit a wider range, with a minimum of -13°C (10°F) and a maximum of 29°C (84°F), leading to an average of 10°C (51°F). The month typically sees moderate precipitation of 30 mm (1.2 in) over about 5 days, accompanied by a relatively low humidity of 46%. Conversely, December brings a significant drop in temperatures, with a minimum of -25°C (-12°F), an average of -9°C (16°F), and a maximum of only 8°C (46°F). Precipitation also increases to 49 mm (1.9 in) over 10 days, and the humidity rises sharply to 87%. This stark contrast highlights the shift from the milder, more variable conditions of early fall to the cold, damp chill characteristic of winter. For a more detailed look at what to expect, check out Sun Valley weather in December.
As September rolls in, Sun Valley experiences a notable transition in its weather, marked by a pleasant mix of warmth and coolness. While summer's warmth lingers, with maximum temperatures reaching the comfortable mid-20s, the crispness of autumn begins to assert itself, bringing cooler nights that can dip into chilly single digits. This month also features a slight uptick in precipitation, usually accompanied by a few more overcast days compared to the sun-drenched summer months. With an average humidity of 46%, the air feels refreshingly cool, making September an ideal time for outdoor adventures. For a deeper dive into the overall weather patterns throughout the year, check out Sun Valley Climate.