September Weather in Duluth, United States

Last updated: February 24, 2025

September in Duluth, United States, presents a transition towards autumn with maximum temperatures reaching 26°C (80°F) and an average of 16°C (62°F), providing mild and pleasant days. However, nights can be quite cool, dipping to a minimum of 4°C (39°F). The month is characterized by a moderate precipitation level of 119 mm (4.7 in) over approximately 12 days, contributing to the region's lush landscape. With an average humidity of 73%, the air feels crisp yet comfortable, making September a delightful time to experience Duluth’s natural beauty.

September Temperature in Duluth

As September rolls into Duluth, a noticeable shift in temperatures marks the transition from summer to autumn. With nighttime temperatures dipping to a mild 4°C (39°F), the crispness in the air begins to signal the end of warmer days. The average temperature sits comfortably around 16°C (62°F), offering a pleasant reprieve from the summer heat, while daytime peaks can reach up to a balmy 26°C (80°F). This month reveals a delightful blend of lingering warmth and the budding coolness of fall, making it a perfect time to enjoy outdoor activities as nature begins its colorful transformation.

September Weather in Duluth: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Duluth, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends.
JanFebMarAprMayJunJulAugSepOctNovDec141427354758666762483323
Data source: Temperature data for Duluth generated using information from the Copernicus Climate Change Service.
Choose your preferred temperature unit
The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Duluth

In September, Duluth experiences a noteworthy uptick in precipitation, with 119 mm (4.7 inches) of rain falling over 12 days, marking it as one of the wetter months of the year. This increase follows a month of substantial rainfall in August, which totaled 109 mm (4.3 inches), suggesting a trend of escalating moisture as summer transitions into fall. The average precipitation days also rise in September, indicating a more frequent, albeit moderate, engagement with the elements. Looking forward, October is poised to continue this pattern with an even higher 153 mm (6.0 inches) of precipitation expected over 13 days, reinforcing the idea that fall in Duluth brings increased rainfall and a shift in atmospheric dynamics.

September Precipitation Trends in Duluth

The chart displays monthly precipitation patterns in Duluth, with values for each month alongside September's data, which is highlighted for easy comparison. It shows the amount of precipitation, providing insights into how September's conditions compare to those of other months.
JanFebMarAprMayJunJulAugSepOctNovDec253453749476961091191535267
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Duluth

As September rolls in, Duluth experiences a slight rise in humidity, with levels reaching 73%. This marks a transition from the summer months, where humidity dipped to its lowest in July at 70% and remained relatively stable through August. Notably, September serves as a bridge to the wetter fall season, with humidity levels beginning to inch back up towards the 80% mark seen in October. This gradual increase sets the stage for the crisp autumn air, which often brings refreshingly brisk days, yet a lingering moisture that hints at the wetter months ahead. The overall pattern illustrates Duluth's characteristic fluctuation in humidity, reflecting the climatic changes that herald the approach of winter.

September Average Humidity in Duluth

This chart illustrates the average monthly humidity levels in Duluth, with September's data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, allowing you to see how September's humidity levels compare to other months.
JanFebMarAprMayJunJulAugSepOctNovDec93%93%89%85%76%71%70%71%73%82%88%91%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Duluth

As September rolls in, Duluth experiences a notable shift in UV Index levels. With a UV Index of 7, the exposure category is classified as high, indicating a moderate risk for harm from unprotected sun exposure. This marks a decrease from the peak summer months, where the UV Index reached 9 in both June and July, necessitating quick skin protection within just 15 minutes. In contrast, September allows for a more forgiving 25 minutes before the risk of sunburn increases, reminiscent of earlier in the season. As the days grow shorter and temperatures begin to dip, residents and visitors alike should still be mindful of UV exposure levels. For detailed information on the UV Index throughout the year, check out Duluth UV Index.

Maximum UV Index Levels in Duluth for September

The chart shows the monthly maximum UV Index (UVI) for Duluth in September, representing the highest UV radiation level. The UVI measures the intensity of ultraviolet radiation from the sun, indicating the potential risk of sunburn and UV-related health issues.
JanFebMarAprMayJunJulAugSepOctNovDec234789987532
Data source: Duluth September UVI data generated using information from the Copernicus Climate Change Service.

UV Risk Categories

  •  Extreme (11+): Avoid the sun, stay in shade.
  •  Very High (8-10): Limit sun exposure.
  •  High (6-7): Use SPF 30+ and protective clothing.
  •  Moderate (3-5): Midday shade recommended.
  •  Low (0-2): No protection needed.

September Sunshine in Duluth

As summer transitions into fall, September in Duluth continues to enjoy a generous amount of sunshine, with 248 hours illuminating the month. This abundance follows a vibrant summer, peaking in July with 355 hours, before gradually tapering off as October approaches. Although September sees a decline from the summer highs, it maintains a significant brightness compared to the earlier months, such as January with a meager 122 hours. This trend showcases Duluth's dynamic seasonal shifts, where the warmth of summer lingers into early autumn, creating a perfect backdrop for outdoor activities and scenic vistas. As the days shorten, the city prepares for a cozy transition into the beautiful hues of fall.

Monthly Sunshine Duration in Duluth: September Highlighted

The September sunshine duration represents the total number of hours Duluth experiences direct sunlight during the month of September, excluding cloudy or obstructed periods. This chart compares the sunshine duration of September with the other months of the year.
JanFebMarAprMayJunJulAugSepOctNovDec122h194h239h239h297h349h355h308h248h188h156h143h
Data source: Duluth September Sunshine duration data generated using information from the Copernicus Climate Change Service.

Chance of Sun in Duluth During September

In Duluth, United States, the likelihood of sunny weather in September stands at a steady 52%, aligning with the sunniest months of summer like June and July. As the seasons shift, September retains a favorable chance for clear skies that readers can appreciate, especially when compared to the gloomier winter months. Interestingly, after peaking in July, there's a gradual decline in sunshine probability, yet September proves to be one of the transitional months that still offers quite a bit of pleasant weather. This makes it an ideal time for outdoor activities, as the lingering warmth of summer complements the crispness of autumn that begins to set in.

Percentage of Sunny Days in September in Duluth

The chart illustrates the percentage of sunny days in Duluth throughout the year, with September highlighted. It highlights the variation in sunshine across each month and provides an overview of the typical frequency of sunny days, offering insights into how often Duluth experiences clear skies throughout the year.
JanFebMarAprMayJunJulAugSepOctNovDec29%42%43%31%47%52%63%58%52%30%36%21%
Data source: Duluth September chance of sun data, generated using information from the Copernicus Climate Change Service.

Daylight Hours in Duluth in September

As the summer sun begins its gradual retreat in September, Duluth experiences a shift in daylight hours, averaging 12 hours a day. This marks a noticeable decline from the 14 hours of light in August, signaling the transition into fall. The pattern reflects a broader trend observed throughout the year in Duluth, where daylight peaks at a lush 15 hours during the summer months of June through July. Following this zenith, daylight wanes steadily, with September providing a gentle reminder of the changing seasons. As the days shorten toward autumn, Duluth’s landscape begins to shift, preparing for the embracing hues of fall while counting down to the crisp, shorter days ahead in October and November.

Average Daylight Hours in Duluth for September

The chart illustrates the variation in daylight duration in Duluth throughout the year, with September highlighted. It shows the monthly changes in daylight hours, calculated by summing the hours between sunrise and sunset.
JanFebMarAprMayJunJulAugSepOctNovDec9h10h 19m11h 57m13h 37m15h 3m15h 47m15h 23m14h 6m12h 29m10h 49m9h 21m8h 35m
Data source: Duluth daylight hours, calculated by summing the hours between sunrise and sunset for each day.

September Winds in Duluth

As September arrives in Duluth, the winds start to pick up slightly, averaging 4.4 m/s (10 mph), reflecting a subtle transition from the calmer breezes of summer. This uptick in wind speed echoes a gradual trend observed throughout the year, where the highest winds occur in the late fall and winter months. July and August witness the lightest winds, with speeds around 3.3 m/s (7 mph) and 4.3 m/s (10 mph), respectively. However, as the days begin to shorten and autumn settles in, the winds start to gain momentum, setting the stage for the brisk, refreshing gusts typical of Duluth's fall weather. This pattern not only enhances the city's distinctive charm but also prepares residents and visitors alike for the vibrant colors and crisp air of the upcoming season.

Average September Wind Speed in Duluth

The chart displays monthly wind speed patterns in Duluth, with values for each month shown alongside September's data, which is highlighted for easy comparison. It illustrates the average wind speed, offering insights into how September's wind conditions compare to the rest of the year.
JanFebMarAprMayJunJulAugSepOctNovDec4.24.75.03.94.03.53.34.34.4 m/s4.35.65.5
Data source: Duluth September wind data, generated using information from the Copernicus Climate Change Service.

How September Weather in Duluth Compares to Other Months

The weather in Duluth 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 Duluth and find detailed weather information for every month.

September and January present stark contrasts in weather. In September, temperatures range from a chilly 4°C (39°F) at night to a warm 26°C (80°F) during the day, with an average of 16°C (62°F). This month experiences considerable precipitation, totaling 119 mm (4.7 in) over approximately 12 days, with humidity levels at 73%. In contrast, January is characterized by frigid conditions, with temperatures dropping to a bone-chilling minimum of -31°C (-24°F) and an average of -10°C (15°F). Despite lower total precipitation at 25 mm (1.0 in) over 6 days, the humidity soars to 93%, contributing to the biting cold. For a detailed look at January weather, check Duluth weather in January.

September and February present stark contrasts in weather conditions. In September, the temperatures range significantly from a chilly 4°C (39°F) at night to a pleasant 26°C (80°F) during the day, with an average of 16°C (62°F). The month also experiences around 119 mm (4.7 in) of precipitation spread over 12 days, and humidity levels hover at 73%. In stark comparison, February is much colder, with temperatures ranging from a frigid -32°C (-25°F) to a maximum of just 8°C (47°F), averaging -10°C (14°F). Precipitation is notably lower in February at 33 mm (1.3 in) over 7 days, but the humidity is higher at 93%. For more details about the chilly conditions in February, you can check Duluth weather in February.

September and March showcase stark contrasts in weather conditions. In September, temperatures range from a brisk 4°C (39°F) at night to a warm 26°C (80°F) during the day, with an average of 16°C (62°F). This month experiences considerable rainfall, totaling 119 mm (4.7 in) over about 12 days, while humidity sits at a comfortable 73%. In contrast, March is characterized by its cold temperatures, with nighttime lows plunging to -22°C (-8°F) and average highs reaching only 10°C (51°F). It sees less precipitation, with 53 mm (2.1 in) falling over about 6 days, and humidity levels are higher at 89%. For a more detailed glimpse into March's chilly conditions, check out Duluth weather in March.

In comparing the weather of September and April, notable differences in temperature and precipitation emerge. September enjoys milder conditions with average temperatures ranging from a minimum of 4°C (39°F) to a maximum of 26°C (80°F), while April experiences cooler temperatures, averaging between -13°C (9°F) and 18°C (65°F). Precipitation levels also differ, with September receiving 119 mm (4.7 in) over 12 days compared to April’s 74 mm (2.9 in) over 10 days. Additionally, April tends to be more humid, averaging 85% humidity compared to September’s 73%. For more detailed information, you can check Duluth weather in April.

When comparing the weather in September and May, we see notable differences in temperature and humidity levels. September offers a milder climate with average temperatures around 16°C (62°F) and maximums reaching up to 26°C (80°F), while May experiences cooler averages at 8°C (47°F) with a similar high of 26°C (79°F). Precipitation is slightly higher in September at 119 mm (4.7 in) over 12 days, compared to May's 94 mm (3.7 in) over 11 days. Humidity is also relatively high in both months, with September at 73% and May at 76%. For a closer look at May's weather, you can check out Duluth weather in May.

In comparing the weather of September and June, we see notable differences in temperature and precipitation patterns. September generally experiences a broader temperature range, with minimums of 4°C (39°F), averages of 16°C (62°F), and maximums reaching 26°C (80°F). In contrast, June has slightly warmer temperatures, starting at a minimum of 5°C (42°F) and peaking at 28°C (82°F), with an average of 15°C (59°F). Precipitation levels also vary, with September receiving 119 mm (4.7 in) over 12 days, compared to June's 76 mm (3.0 in) over just 9 days. Humidity levels are similar for both months, hovering around 73% for September and 71% for June. For a more detailed overview of June weather, you can check out Duluth weather in June.

In comparing the weather patterns of September and July, we observe notable differences in temperature and precipitation. September experiences a broader temperature range, with minimums dipping to 4°C (39°F) and maximums reaching 26°C (80°F), resulting in an average of 16°C (62°F). In contrast, July maintains warmer conditions with minimums at 11°C (53°F) and an average temperature of 19°C (66°F), peaking at 27°C (82°F). Additionally, September sees more precipitation, totaling 119 mm (4.7 in) over 12 days, compared to July's 95 mm (3.8 in) spread across just 8 days. This results in a slightly higher humidity level in September at 73%, whereas July registers at 70%. For more detailed insights, you can check Duluth weather in July.

September generally experiences cooler temperatures compared to August, with a minimum temperature of 4°C (39°F) contrasting sharply with August's milder low of 13°C (55°F). The average temperature in September is slightly lower at 16°C (62°F) compared to August's 19°C (67°F), although the maximum temperatures remain similar, with September peaking at 26°C (80°F) and August at 27°C (82°F). Precipitation in September is slightly higher at 119 mm (4.7 in) over 12 days, compared to August’s 109 mm (4.3 in) over 11 days, indicating a wetter month as summer transitions into fall. Humidity levels are comparable, with September at 73% and August at 71%. For more detailed insights into August weather, visit Duluth weather in August.

In September, the weather tends to be milder, with average temperatures ranging from a minimum of 4°C (39°F) to a maximum of 26°C (80°F). The month receives about 119 mm (4.7 in) of precipitation over 12 days, with a humidity level of 73%. In contrast, October brings a noticeable chill, with temperatures dipping to a minimum of -5°C (24°F) and an average of 9°C (48°F), peaking at 22°C (71°F). Precipitation increases slightly, totaling 153 mm (6.0 in) across 13 days, accompanied by a higher humidity of 81%. For more detailed insights into October conditions, check out Duluth weather in October.

In September, the weather is generally milder, with temperatures ranging from a minimum of 4°C (39°F) to a maximum of 26°C (80°F), offering an average of 16°C (62°F). This month experiences around 119 mm (4.7 in) of precipitation over 12 days, alongside a humidity level of 73%. In contrast, November brings a significant drop in temperatures, with a minimum of -12°C (11°F) and an average of only 1°C (34°F), reaching a maximum of 17°C (63°F). Precipitation decreases to 52 mm (2.0 in) over 10 days, but humidity rises to 87%, creating a stark difference between the two months. For more detailed information, check out Duluth weather in November.

September and December present starkly contrasting weather patterns. In September, the temperatures range from a mild 4°C (39°F) at night to a pleasant maximum of 26°C (80°F) during the day, with an average of 16°C (62°F). The month experiences considerable rainfall, with 119 mm (4.7 in) over approximately 12 days, accompanied by a humidity level of 73%. In contrast, December brings frigid conditions with temperatures plummeting to a minimum of -26°C (-15°F) and averaging -5°C (23°F). The maximum temperature barely reaches 9°C (48°F), and while the precipitation decreases to 67 mm (2.6 in) over 10 days, the humidity rises to a chilly 91%. For more details, you can check out Duluth weather in December.

Compare Duluth's Climate with Cities Worldwide

Conclusion: What to Expect From September Weather in Duluth

As September unfolds in Duluth, the transition from summer to fall becomes evident, marked by a noticeable drop in temperatures compared to the warmer months. While the maximum daytime highs can still reach a comfortable 26°C (80°F), the overall climate shifts towards cooler averages, with nights dipping to a brisk 4°C (39°F). With frequent showers adding up to 119 mm of rain over about half the month, the air feels notably more humid at 73%, contrasting sharply with the drier, sunnier days of summer. This blend of warmth and moisture, combined with the crispness of early autumn, makes September a unique experience in Duluth. For a deeper dive into the city’s shifting climate, visit Duluth Climate.