Last updated: February 24, 2025
September in Thermopolis, United States, presents a fascinating climate profile, characterized by a broad temperature range that peaks at a maximum of 37°C (100°F), while dipping to a minimum of -4°C (24°F). The average temperature hovers around a comfortable 17°C (62°F), making it an appealing month for outdoor activities. However, residents and visitors should be prepared for some variability, as 27 mm (1.0 in) of rain falls over just three days, contributing to a humidity level of 59%. This blend of warmth and occasional showers creates a dynamic environment perfect for enjoying the transitional beauty of early autumn in the region.
In September, Thermopolis experiences a notable shift in temperatures, as summer begins to fade and autumn approaches. With minimum temperatures hovering around -4°C (24°F) and average highs reaching a comfortable 37°C (100°F), the month offers a delightful mix of warmth and coolness. This transitional period features an average temperature of 17°C (62°F), providing residents and visitors alike with pleasant days perfect for outdoor activities. As the region makes its gradual descent into the cooler months ahead, September becomes a sweet farewell to the sweltering heat of summer, showcasing the stunning contrasts that define this charming part of the United States.
In September, Thermopolis experiences a modest precipitation increase, with 27 mm (1.0 in) of rainfall spread over just three days. This aligns with the late-summer transition to autumn, exhibiting a trend where rainfall begins to pick up compared to the preceding months of July and August, which recorded significantly lower amounts. The consistency in precipitation—matching October's rainfall of 27 mm (1.1 in)—suggests a stable weather pattern as the region heads into fall. Overall, September stands as a pivotal month, with its rainfall heralding the change of seasons while maintaining a balance in the area's hydrological cycle.
As summer transitions into fall, September in Thermopolis marks a notable shift in humidity, maintaining a low and comfortable 59%, the same level seen in August. This trend signifies a steady decline from the high humidity levels typical of winter months, where figures hover around 90% in January and February. The gradual decrease becomes more pronounced from May onward, culminating in one of the driest months of the year. With the humidity stabilizing at 59%, residents can enjoy crisp, refreshing air, making September an ideal time for outdoor activities as nature begins to hint at the upcoming autumn.
As September rolls in, Thermopolis experiences a UV Index of 9, placing it in the very high exposure category, with a burn time of just 15 minutes. This trend continues from the intense summer months, where the UV Index peaked at 11. While September marks a slight decline compared to August, which held a UV Index of 10, it still requires caution. Notably, the UV levels remain significantly elevated compared to earlier months, signaling the need for protective measures as outdoor activities are enjoyed. For those planning to bask in the sun, staying informed about the UV Index is crucial. For more detailed information, visit Thermopolis UV Index.
UV Risk Categories
September in Thermopolis, United States, shines brightly with 301 hours of sunshine, marking a graceful transition from the sun-drenched days of summer to the cooler fall months. As the year progresses, we see a steady increase in sunlight from January's modest 169 hours to July's peak of 391 hours, making summer the undeniable champion of bright days. However, September maintains its charm with nearly 75% of July's sunshine, showcasing a lingering warmth that invites both residents and visitors to soak in the golden hues. As we move toward October, where sunlight dips to 260 hours, September serves as a delightful reminder of summer's abundance before the embrace of autumn's softer light begins.
As September rolls around in Thermopolis, the likelihood of sunshine significantly increases, boasting a 74% chance of clear skies. This marked rise follows the summer months, where sunlit days in June, July, and August maintain a comfortable range between 65% and 68%. Transitioning into autumn, September stands out as a standout month for sun enthusiasts, eclipsing the earlier months of the year, which generally struggle to reach the 50% threshold. With such promising prospects for sunny days, September emerges as an ideal time to bask in the warmth before the cooler months set in.
As September unfolds in Thermopolis, the daylight hours begin to wane, with the sun gracing the sky for about 12 hours each day. This transitional month follows the sunniest days of summer, where July and June basked in 15 hours of daylight, offering long, bright evenings perfect for outdoor activities. As autumn approaches, daylight gradually diminishes, moving from 14 hours in May to 12 hours now, signaling a shift in the season. Following September, the daylight hours will continue to decrease, dropping to 10 hours in October, reflecting the steady descent into the winter months. This ebb and flow of daylight not only marks the changing seasons but also sets the stage for the cozy, reflective ambiance of fall that many cherish.
In September, Thermopolis experiences a gentle breeze, with an average wind speed of 2.6 m/s (6 mph), consistent with the lighter winds of late summer. As the month transitions, the wind speed holds steady, mirroring the patterns seen in the preceding months of August and October, which also register the same mild speeds. This slight stability in wind conditions suggests a seasonal calmness, signaling the approach of fall. Notably, while April and June peak at 3.2 m/s and 3.0 m/s respectively, the overall trend shows that the winds ease as the year progresses toward winter, culminating in November's gentle drop to 2.4 m/s. Thus, September marks a bridge between warmer, breezier months and the cooler, stiller seasons ahead.
The weather in Thermopolis 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 Thermopolis and find detailed weather information for every month.
September and January present strikingly contrasting weather conditions. In September, temperatures can soar from a chilly minimum of -4°C (24°F) to an average of 17°C (62°F), peaking at a hot 37°C (100°F). The month experiences modest precipitation, averaging 27 mm (1.0 in) over three days and with a humidity level of 59%. In contrast, January is much colder, with temperatures plunging to a minimum of -29°C (-20°F) and averaging around -6°C (21°F), with a maximum of only 11°C (52°F). This winter month is drier, with just 11 mm (0.4 in) of precipitation over two days, but with a notably higher humidity of 90%. For more detailed insights into January weather, visit Thermopolis weather in January.
When comparing the weather in September and February, it’s clear that these months present stark contrasts. September boasts milder temperatures, with a minimum of -4°C (24°F) and a comfortable average of 17°C (62°F), peaking at a warm 37°C (100°F). This month experiences relatively low precipitation, averaging 27 mm (1.0 in) over just 3 days, and the humidity is around 59%. In contrast, February chill descends with much colder temperatures, dipping to a minimum of -25°C (-13°F) and an average of -6°C (21°F), with a maximum of only 14°C (57°F). The month sees slightly lower precipitation at 21 mm (0.8 in), but over a higher number of days at 6, and the humidity rises significantly to 89%. For those curious about Thermopolis weather specifics during February, additional details can be found here: Thermopolis weather in February.
In September, temperatures vary considerably, with lows around -4°C (24°F) and highs reaching up to 37°C (100°F), resulting in an average of 17°C (62°F). The month experiences relatively low precipitation at 27 mm (1.0 in) over just 3 days, with humidity at 59%. In contrast, March presents much cooler conditions, with minimum temperatures plummeting to -27°C (-16°F) and an average of only 3°C (37°F). The maximum temperature in March is significantly lower at 24°C (76°F), accompanied by slightly less precipitation at 22 mm (0.9 in) but spread over more days, totaling 5. Additionally, humidity is higher in March at 82%. For more detailed information about the weather in March, you can visit Thermopolis weather in March.
When comparing the weather in September and April, notable contrasts emerge. September typically showcases a wide temperature range, with minimums around -4°C (24°F) and maximums soaring to 37°C (100°F), averaging 17°C (62°F). In contrast, April experiences cooler temperatures, ranging from a minimum of -15°C (5°F) to a maximum of 27°C (80°F), leading to a much lower average of 7°C (44°F). Additionally, April sees more precipitation with 53 mm (2.1 in) spread across 9 days, compared to September’s 27 mm (1.0 in) over just 3 days. The humidity is also higher in April at 72%, compared to September’s 59%. For more detailed information on the weather in April, you can visit Thermopolis weather in April.
In comparing the weather of September and May, notable differences emerge in both temperature and precipitation patterns. September boasts a broader temperature range, with a maximum reaching up to 37°C (100°F) and an average of 17°C (62°F). In contrast, May exhibits calmer temperatures, peaking at 31°C (88°F) and averaging 12°C (54°F). Precipitation also varies significantly, with September receiving only 27 mm (1.0 in) over three days, while May experiences higher rainfall of 67 mm (2.6 in) spread over ten days. Additionally, humidity is slightly higher in May at 69%, compared to September's 59%. For a detailed look at the conditions during this month, you can visit Thermopolis weather in May.
September weather tends to exhibit a broader temperature range compared to June, with minimums dipping to -4°C (24°F) and maximums soaring up to 37°C (100°F). In contrast, June starts warmer with a minimum of 1°C (35°F) and can reach a peak temperature of 39°C (103°F). Both months experience similar levels of precipitation, with September and June receiving approximately 27 mm (1.0 in and 1.1 in, respectively), though June has more rainy days at six compared to September's three. Additionally, humidity levels are higher in June at 67%, compared to 59% in September. For more details on June's weather conditions, you can check Thermopolis weather in June.
In comparing the weather of September and July, September experiences a broader temperature range, with minimums dropping to -4°C (24°F) while averaging around 17°C (62°F) and peaking at 37°C (100°F). In contrast, July has a milder minimum temperature of 7°C (44°F) and a higher average of 24°C (76°F), reaching a maximum of 40°C (104°F). Additionally, September sees slightly more precipitation, with an average of 27 mm (1.0 in) over three days, compared to July's 13 mm (0.5 in) within just two days. The humidity levels are also notable, with September at 59% and July slightly higher at 65%. For more details on the July weather, you can check Thermopolis weather in July.
In comparing the weather between September and August, September experiences a wider temperature range, with lows dropping to -4°C (24°F) and high reaching up to 37°C (100°F), while August maintains a milder minimum temperature of 7°C (44°F) and a similar maximum of 38°C (100°F). The average temperature in September is around 17°C (62°F), which is slightly cooler than August's average of 22°C (72°F). Although both months see similar precipitation levels, with September receiving 27 mm (1.0 in) and August 18 mm (0.7 in), they both have three days of rainfall and humidity remains consistent at 59%. For a detailed look at August weather, you can check Thermopolis weather in August.
In September, temperatures range significantly, with a minimum of -4°C (24°F) and a maximum reaching as high as 37°C (100°F), resulting in an average of 17°C (62°F). The month experiences relatively low precipitation of 27 mm (1.0 in) over just 3 days and maintains a humidity level of 59%. In contrast, October presents a marked drop in temperatures, boasting a minimum of -22°C (-8°F) and a maximum of 28°C (83°F), bringing the average down to 7°C (44°F). Precipitation slightly increases to 27 mm (1.1 in) but occurs over 6 days, with an uptick in humidity to 69%. For more detailed insights, check out the Thermopolis weather in October.
September and November present stark contrasts in weather conditions. September boasts a wide temperature range, with minimums reaching -4°C (24°F) and maximums soaring to 37°C (100°F), culminating in a comfortable average of 17°C (62°F). The month experiences limited precipitation, totaling 27 mm (1.0 in) over just three days, along with a moderate humidity level of 59%. In comparison, November sharply declines in temperature, featuring minimums of -16°C (4°F) and a much cooler average of 1°C (35°F), with maximums peaking at 21°C (70°F). While precipitation is lower at 17 mm (0.7 in), it spreads over four days, and humidity rises significantly to 83%. For more detailed insights, check out Thermopolis weather in November.
In September, temperatures can range significantly, with minimums dipping to -4°C (24°F) while averaging around a comfortable 17°C (62°F) and peaking at a scorching 37°C (100°F). The month typically sees low precipitation of 27 mm (1.0 in) over just three days and maintains a humidity level of 59%. In contrast, December brings a much colder climate, with temperatures plunging to a minimum of -25°C (-12°F) and an average of -4°C (24°F), reaching up to only 18°C (65°F) at the warmest. Precipitation decreases to 14 mm (0.6 in) spread over four days, and humidity spikes to 89%. For more specifics on December conditions, you can explore Thermopolis weather in December.
Overall, the dramatic shift in temperature and humidity between these two months illustrates the transition from the warm tail end of summer to the frigid depths of winter.
September in Thermopolis marks a distinct transition from the sweltering summer heat to the crispness of autumn. With temperatures oscillating dramatically—where daytime highs flirt with summer extremes while nights can plunge into chilly territory—the month's weather embodies a fascinating contrast. Precipitation makes a brief appearance, allowing for rejuvenation but remaining minimal compared to other months, which tend to experience heavier rainfall. The average humidity level adds a touch of mugginess, making this month feel unique amongst the seasons. As nature prepares for the cooler months ahead, September serves as a beautiful bridge between the warmth of summer and the refreshing embrace of fall. For further insights, explore the full details of the Thermopolis Climate.