Last updated: February 24, 2025
In September, Denver experiences a dynamic shift in weather, with maximum temperatures soaring up to 36°C (98°F) while the average hovers around a comfortable 19°C (66°F). As temperatures dip, the minimum can reach a brisk -2°C (30°F), highlighting the transition to autumn. This month sees an average precipitation amount of 29 mm (1.2 in) spread over approximately 5 days, contributing to a humidity level of 65%. Overall, September in Denver is characterized by its warm days that gradually give way to cooler evenings, setting the stage for the vibrant fall season ahead.
September in Denver ushers in the transition from summer's heat to the crispness of autumn. With nighttime temperatures dipping to an average minimum of -2°C (30°F), it’s a cooling reprieve after the sweltering summer months, where highs still reach up to 36°C (98°F). The average temperature stabilizes around 19°C (66°F), offering delightful days filled with sunshine and vibrant fall foliage. This month marks a significant shift, as the warm weather gradually fades, paving the way for October’s chill. Overall, September is a perfect blend of lingering warmth and the first hints of fall, making it an ideal time to explore the scenic outdoors in Denver.
In September, Denver experiences a gentle transition from summer to fall, marked by an average precipitation of 29 mm (1.2 in) over approximately 5 days. This amount follows a gradual decline from the wetter months of May and June, which peak at 111 mm (4.4 in) and 48 mm (1.9 in) respectively. While September’s rain is less frequent than the summer months, it plays a crucial role in replenishing the soil, setting the stage for the dry autumn ahead. The overall trend showcases a steady decrease in rainfall as the year progresses, with September acting as a bridge between the lush summer and the drier fall, creating an inviting atmosphere as the leaves begin to change color.
As summer transitions into autumn, September in Denver brings a refreshing change in humidity levels, settling around 65%. This month marks a slight uptick from the drier summer months of July and August, when humidity dipped to 52% and 56%, respectively. Overall, the trend reveals a consistent decline in humidity from the peak of winter months, with January’s 88% giving way to the crisp, more comfortable texture of mid-fall. This seasonal shift not only enhances outdoor activities but also offers a pleasant reprieve before the winter months, where humidity levels rise once again, peaking at 89% in December. As such, September serves as a transitional phase, perfectly balancing the fading warmth of summer with the cool embrace of autumn.
As summer transitions to autumn in Denver, the September UV Index showcases a notable shift, registering at 10 which places it in the very high exposure category. This marks a slight plunge from the peak levels during the summer months, yet it still requires vigilance. With a burn time of just 15 minutes, residents and visitors should remain aware that sun protection is essential. Notably, while September's index indicates a decrease from the extreme highs of July and August, it remains considerably elevated compared to early months in the year. This trend illustrates how sunlight intensity can persist even as cooler weather approaches, urging a proactive approach to sun safety. For further insights and real-time updates, check out Denver UV Index.
UV Risk Categories
As the summer sun begins its gradual descent in September, Denver still enjoys a substantial 310 hours of sunshine, providing a pleasant transition into fall. This month reflects a slight decrease from the peak of 375 hours in July, yet it stands strong compared to the colder months ahead. The sunshine hours in September are part of a broader trend, where the city experiences an impressive increase in daylight from the short, gray days of January, which see only 187 hours. Notably, from March onward, sunshine hours consistently climb, peaking during the summer while maintaining a robust presence into early autumn. This seasonal shift not only enhances outdoor activities but also invites residents and visitors alike to revel in the warm glow before winter takes hold.
In September, Denver enjoys a notable increase in the likelihood of sunny weather, with a 69% chance of sun. This marks a peak in the late summer season, following August’s 67% and preceding the slightly diminished prospects of October at 67%. Furthermore, the trend indicates a gradual rise from the earlier months of the year, where the sunniest chances hover around the low to mid-50s%. As the summer heat wanes, September's sunny days provide a perfect backdrop for outdoor activities, making it a delightful time to experience the vibrant fall colors in the area. With clear skies and pleasant temperatures, Denverites and visitors alike can revel in the beauty of the changing season.
As September unfolds in Denver, the city experiences a gentle transition in daylight duration, with the sun gracing the skies for 12 hours each day. This month marks a noticeable shift as daylight begins to wane from the peak of summer; August still enjoyed 13 hours of sunlight. Following a steady increase from the depths of winter, where daylight barely reaches 9 hours in January, the gradual tapering in September signals the approach of fall. This gradual decrease in sunlight highlights a rhythmic pattern, where longer days of up to 14 hours during the summer months give way to shorter durations as the year progresses. As the vibrant hues of autumn begin to paint the landscapes, Denverites relish the warm days of early fall while preparing for the cozy, shorter days that lie ahead.
As September sweeps through Denver, the breeze maintains a steady average wind speed of 2.4 m/s (5 mph), mirroring the gentle gusts of both May and July. This month serves as a transitional stage, where summer's warmth begins to recede, yet the winds remain consistent, contributing to the crispness in the air. Notably, September’s winds continue the trend seen earlier in the summer months, with speeds slightly lower than those experienced in the autumn months ahead, such as October and November, which typically see a gradual uptick. As the season shifts, these mild winds create a refreshing atmosphere, ideal for outdoor activities and the delightful change in foliage.
The weather in Denver 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 Denver and find detailed weather information for every month.
September and January present starkly different weather conditions. In September, the temperature ranges from a chilly minimum of -2°C (30°F) to a warm maximum of 36°C (98°F), with an average of 19°C (66°F). The month sees about 29 mm (1.2 in) of precipitation over approximately 5 days, and humidity levels hover around 65%. Conversely, January is much colder, with temperatures dropping to a minimum of -23°C (-10°F) and reaching a maximum of 19°C (67°F), averaging at -1°C (31°F). Precipitation is slightly less, at 23 mm (0.9 in) over 4 days, but the humidity is higher at 88%. For more details about January weather, you can check Denver weather in January.
September typically offers a much milder climate compared to February, with average temperatures ranging from a chilly minimum of -2°C (30°F) to a warm maximum of 36°C (98°F). In contrast, February is much colder, with temperatures plummeting to a minimum of -25°C (-12°F) and averaging around -1°C (30°F). Both months see similar levels of precipitation, approximately 29 mm, but February experiences slightly higher humidity at 87% compared to September's 65%. For more details on what to expect during February, check out Denver weather in February.
September and March exhibit strikingly different weather patterns. In September, temperatures range from a minimum of -2°C (30°F) to a comfortable average of 19°C (66°F), peaking at a sweltering 36°C (98°F). The month sees relatively low precipitation at 29 mm (1.2 in) over five days, with humidity around 65%. In contrast, March is significantly chillier, with temperatures dipping as low as -20°C (-5°F) and averaging only 4°C (40°F), while reaching a maximum of 27°C (80°F). Precipitation is higher in March, totaling 57 mm (2.3 in) across nine days, and the humidity spikes to 81%. For more details, check out Denver weather in March.
In comparing the weather of September and April, we see notable differences. September experiences a wide temperature range, with minimums of -2°C (30°F) and maximums reaching up to 36°C (98°F), averaging around 19°C (66°F). The month has relatively low precipitation at 29 mm (1.2 in) over just 5 days, accompanied by a humidity level of 65%. In contrast, April is cooler, with temperatures ranging from a minimum of -14°C (8°F) to a maximum of 29°C (84°F), averaging only 8°C (47°F). It sees more rainfall, totaling 55 mm (2.2 in) over 10 days, and has a higher humidity level at 76%. For more detailed information on this month, check out Denver weather in April.
When comparing the weather in September to that of May, there are notable differences in temperature and precipitation. September features a wider temperature range, with minimums around -2°C (30°F) and maximums reaching up to 36°C (98°F), while May's temperatures typically vary from a minimum of -6°C (21°F) to a maximum of 33°C (91°F). Additionally, September experiences significantly less precipitation, averaging only 29 mm (1.2 in) over about 5 days, compared to May's wetter climate with 111 mm (4.4 in) over 14 days. Despite the humidity levels being quite similar at around 65-66%, the overall weather patterns indicate that September tends to be warmer and drier than May. For a more detailed look at May weather, you can visit Denver weather in May.
In comparing the weather of September and June, September generally experiences a wider temperature range, with minimums dropping to -2°C (30°F) and maximums reaching up to 36°C (98°F), while June's temperatures start off higher, with minimums at 5°C (42°F) and maximums peaking at 37°C (99°F). Precipitation in September is lower, totaling 29 mm (1.2 in) over just 5 days, compared to June's 48 mm (1.9 in) across 9 days. Additionally, September has a slightly higher humidity level at 65%, whereas June is a bit more comfortable at 58%. For a detailed look at June weather in Denver, you can visit Denver weather in June.
Comparing the weather in September and July reveals distinct differences in temperature and precipitation patterns. In July, temperatures range from a minimum of 10°C (51°F) to a maximum of 36°C (98°F), with an average of 23°C (74°F). It experiences higher humidity at 52% and more rainfall, totaling 43 mm (1.7 in) over approximately 9 days. In contrast, September features a wider temperature range, with minimums dropping to -2°C (30°F) and an average of 19°C (66°F), while still reaching the same maximum of 36°C (98°F). September also sees lower precipitation levels at 29 mm (1.2 in) over 5 days and higher humidity at 65%. For more detailed insights into July weather, you can visit Denver weather in July.
September's weather presents a distinct shift compared to August. While both months share a maximum temperature of 36°C (98°F), September experiences a broader range with a minimum of -2°C (30°F) compared to August's milder 10°C (50°F). Average temperatures also drop slightly, from 22°C (72°F) in August to 19°C (66°F) in September. Precipitation is slightly lower in September at 29 mm (1.2 in) over 5 days, compared to 35 mm (1.4 in) over 7 days in August. Humidity remains higher in September at 65%, reflecting a shift from the drier conditions of August, which had a humidity of 56%. For more detailed comparisons, you can check Denver weather in August.
September and October showcase a significant contrast in weather patterns. In September, temperatures range from a minimum of -2°C (30°F) to a maximum of 36°C (98°F), offering an average of 19°C (66°F) and relatively moderate humidity at 65%. Precipitation is low, with only 29 mm (1.2 in) recorded over 5 days. Conversely, October brings cooler temperatures, with a minimum of -18°C (1°F), an average of 9°C (49°F), and a maximum of 30°C (86°F). The month also sees an increase in precipitation to 37 mm (1.5 in) spread across 7 days, along with higher humidity levels at 76%. For more information on October's weather in particular cities, check out Denver weather in October.
September and November present markedly different weather patterns. September showcases a more temperate climate, with average temperatures around 19°C (66°F) and maximums reaching a scorching 36°C (98°F), accompanied by relatively low precipitation of 29 mm (1.2 in) over 5 days and humidity levels at 65%. In contrast, November brings a significant chill, with average temperatures dropping to 5°C (41°F) and minimums plunging as low as -16°C (3°F). Although it receives a slightly lower total precipitation of 24 mm (1.0 in) across 4 days, the increased humidity at 82% adds to the crispness of the air. For more detailed information, check out Denver weather in November.
In September, temperatures in Denver can vary significantly, ranging from a chilly -2°C (30°F) at night to a warm 36°C (98°F) during the day, with an average of 19°C (66°F). The month experiences around 29 mm (1.2 in) of precipitation over five days, and the humidity sits at 65%. In contrast, December brings much colder weather, with temperatures dropping to a minimum of -19°C (-1°F) and reaching a maximum of 22°C (72°F), resulting in an average temperature of just 1°C (34°F). Precipitation decreases to 14 mm (0.6 in) across three days, while humidity rises significantly to 89%. For a detailed look at weather patterns during this winter month, check out Denver weather in December.
As summer gracefully transitions into fall, September in Denver brings a delightful mix of warm and cool temperatures, making it distinct from both the stifling heat of summer and the crisp chill of autumn. With daytime highs reaching up to 36°C (98°F) and cooler nights dipping to -2°C (30°F), this month showcases the city’s diverse weather patterns. Precipitation is relatively minimal, with only a few days of rain, allowing for plenty of opportunities to explore the outdoors. The average humidity of 65% adds a subtle softness to the air, providing a refreshing contrast to the dry summer months. For a deeper understanding of what to expect, check out Denver Climate.