Last updated: February 24, 2025
September in Portland, United States, offers a delightful blend of moderate temperatures and refreshing autumnal ambiance. The maximum temperature reaches a pleasant 26°C (79°F), while the average hovers around 17°C (63°F), providing a comfortable climate for outdoor activities. With minimums falling to 8°C (46°F), mornings can be brisk but invigorating. This month sees 77 mm (3.0 in) of precipitation over approximately 8 days, maintaining the city's lush greenery. Humidity levels at 71% contribute to the crispness of the air, making September an ideal time to explore Portland's vibrant parks and scenic vistas.
As summer transitions to fall, September in Portland, United States offers a delightful reprieve with mild temperatures that reflect the changing season. The month starts with a minimum temperature of 8°C (46°F), providing a refreshing crispness to the air, while the average warms to a pleasant 17°C (63°F). With daytime highs reaching up to 26°C (79°F), residents and visitors can enjoy ample sunshine before the cooler months set in. This gentle shift from the humid warmth of summer, where temperatures often peak around 28°C (83°F), begins to nurture a more temperate feel, setting the stage for cozy autumn days to come. As the month unfolds, the blend of warm afternoons and cooler evenings invites outdoor exploration amidst Portland’s beautiful fall foliage.
In September, Portland experiences a notable shift in precipitation patterns as summer draws to a close. The city receives 77 mm (3.0 in) of rainfall over 8 days, marking a transition from the drier months of July and August, which saw 123 mm (4.9 in) and 75 mm (3.0 in), respectively. This gradual increase in precipitation signals the onset of the fall season, as rainfall begins to pick up, paving the way for the wetter months ahead. While September's totals are relatively moderate, they foreshadow the more significant downpours that characterize October, where average precipitation leaps to 163 mm (6.4 in). Overall, this month serves as a gentle reminder of the changing weather, setting the stage for the lush, vibrant landscapes that Portland is known for in the autumn.
As summer fades, September in Portland brings a noticeable shift in humidity, averaging 71%. This marks a slight increase from the previous months; with August recording the lowest point of 66%, September signifies the return of more moisture in the air. The transition from the drier warmth of summer to the more humid autumn is gradual, reflecting a broader climatic trend for the region. Following the peak of summer dryness, humidity levels begin to rise again heading into October, where they reach 78%, reminiscent of the higher values seen earlier in the year. Thus, September serves as a pivotal bridge, welcoming the cooler, more humid months ahead.
As summer transitions into fall, the UV Index in Portland remains notably high in September, registering a value of 7—indicating a high exposure category. This level reflects a slight decrease from the extreme heights of the previous months but still warrants caution, with a burn time of just 25 minutes for unprotected skin. Throughout the year, Portland's UV levels illustrate a clear trend: from the low values of winter to the sharp peak of summer, the UV Index gradually declines as autumn approaches. While it’s essential to enjoy the beautiful September days, don’t forget to protect your skin! For more detailed insights, visit Portland UV Index.
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As summer gives way to autumn, September in Portland continues to bask in ample sunshine, boasting an impressive 288 hours of sunlight. This delightful month holds onto the sunny spell, following the peak of July and August, which recorded 333 and 336 hours, respectively. The gradual decline in sunlight as the year progresses is evident, yet September still showcases a robust vitality, surpassing every month from January to April. With the golden hues of early fall and the lingering warmth of summer, this month offers the perfect backdrop for outdoor adventures and soaking in the beauty of Portland's changing landscape. Thus, while the days grow shorter, September remains a radiant bridge between two vibrant seasons.
In September, Portland experiences a 43% chance of sunny weather, marking a slight uptick from the summer months where sunny days dip to their lowest in July and August at 29% and 33%, respectively. This trend indicates a gradual shift as the city transitions into fall, with the chances of sun in September being more favorable than during the peak of summer. Interestingly, the likelihood of sunshine also trails into the autumn months, as October sees a decrease to 37%, before rebounding with higher percentages in November at 54%. This ebb and flow of sunshine reflects the dynamic weather patterns of the Pacific Northwest—where September can often be a golden month, inviting residents and visitors alike to soak in the last warmth before winter begins to set in.
As September arrives in Portland, the city transitions into a new rhythm, marked by a slight decrease in daylight. With 12 hours of light, this month signals the beginning of autumn, following the peak of long days in June and July, which boasted 15 hours of daylight. The gradual reduction from summer's brightness reflects the shifting seasons, as the impressive 14 hours in May and 13 hours in August give way to shorter days, beckoning cooler weather and vibrant fall leaves. This natural ebb and flow in daylight not only enhances the beauty of the Portland landscape but also invites residents to savor outdoor activities before the days shorten further into 10 hours by October.
As September arrives in Portland, the average wind speed gently picks up to 4.0 m/s (9 mph), a moderate breeze that stirs the air after the calm of summer months. This transition from the summer lull, where wind speeds dipped to their lowest in July and August at 3.4 m/s (8 mph) and 3.3 m/s (7 mph) respectively, heralds the return of more dynamic conditions. Compared to the bustling spring months, where winds reached a peak of 5.3 m/s (12 mph) in March, September's winds offer a soothing embrace, perfectly complementing the changing foliage and warm afternoons. As we move towards October, where speeds slightly increase to 4.2 m/s (9 mph), the winds in Portland play a vital role in ushering in the vibrant autumn, reminding us of the beautiful, shifting seasons.
The weather in Portland 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 Portland and find detailed weather information for every month.
September and January present starkly different weather patterns. In September, temperatures range from a mild 8°C (46°F) at night to a comfortable average of 17°C (63°F) during the day, peaking at a maximum of 26°C (79°F). The month experiences moderate rainfall of 77 mm (3.0 in) over about 8 days, with humidity levels around 71%. In contrast, January is characterized by much colder conditions, with temperatures plummeting to a minimum of -19°C (-2°F) and an average of -2°C (28°F), reaching a maximum of just 12°C (54°F). During this winter month, precipitation increases slightly to 97 mm (3.8 in) over 9 days, and humidity rises to 86%. For more details, you can check out Portland weather in January.
September and February present starkly contrasting weather conditions. In September, temperatures range from a mild 8°C (46°F) at night to a pleasant high of 26°C (79°F) during the day, with an average temperature of 17°C (63°F). This month sees about 77 mm (3.0 in) of precipitation over approximately 8 days, with humidity around 71%, creating a comfortable, early autumn atmosphere. In sharp contrast, February brings much colder temperatures, with lows plummeting to -17°C (2°F) and highs reaching just 14°C (57°F), averaging -2°C (29°F). This month experiences more precipitation at 103 mm (4.1 in) over around 10 days, combined with higher humidity at 84%, resulting in a much harsher winter environment. For more specifics, you can check Portland weather in February.
September and March present stark contrasts in weather patterns. In September, temperatures range from a mild 8°C (46°F) at night to a comfortable 26°C (79°F) during the day, while March experiences much colder conditions, with temperatures plunging as low as -15°C (6°F) and only reaching a maximum of 13°C (56°F). Precipitation levels are relatively high in both months, with September receiving 77 mm (3.0 inches) over 8 days and March slightly wetter at 91 mm (3.6 inches) over 9 days. Additionally, March tends to be more humid, with humidity levels reaching 82%, compared to September's 71%. For a more detailed look at the weather in March, you can check Portland weather in March.
September and April present quite different weather patterns. September boasts a milder climate with temperatures ranging from a minimum of 8°C (46°F) to a maximum of 26°C (79°F), averaging around 17°C (63°F). In contrast, April's temperatures are noticeably cooler, starting at a minimum of -3°C (27°F) and peaking at 18°C (65°F) with an average of 6°C (43°F). Additionally, April experiences significantly more precipitation, with 149 mm (5.9 in) over 13 days compared to September's 77 mm (3.0 in) over 8 days. The humidity is slightly higher in April at 80%, compared to September's 71%. For a more detailed look at conditions in April, you can check Portland weather in April.
In comparing the weather of September and May, we observe notable differences in temperature and precipitation patterns. September tends to be warmer, with average temperatures ranging from a minimum of 8°C (46°F) to a maximum of 26°C (79°F), while May has cooler averages, with temperatures ranging from 2°C (36°F) to 24°C (76°F). Precipitation is also a factor, as September receives around 77 mm (3.0 in) over about 8 days, compared to May's 94 mm (3.7 in) spread over 10 days. Interestingly, both months exhibit similar humidity levels, with September at 71% and May at 72%. For more detailed insights about May weather in Portland, you can refer to Portland weather in May.
When comparing the weather in September and June, both months exhibit a similar temperature range, with minimums around 8°C (46-47°F) and average temperatures close to 17°C (63-62°F). However, June typically enjoys a slightly warmer maximum temperature of 28°C (83°F) compared to September's 26°C (79°F). Precipitation levels are comparable in both months, with September receiving 77 mm (3.0 in) over 8 days and June slightly higher at 80 mm (3.2 in) across 9 days. The humidity remains consistent, hovering around 71-72%. For a more detailed look at June conditions, visit Portland weather in June.
In comparing the weather between September and July, September tends to be cooler with temperatures ranging from a minimum of 8°C (46°F) to a maximum of 26°C (79°F), averaging around 17°C (63°F). In contrast, July is warmer, featuring a minimum of 13°C (56°F) and a maximum of 28°C (83°F), with an average temperature of 20°C (68°F). Additionally, September experiences 77 mm (3.0 in) of precipitation over approximately 8 days, whereas July receives more rainfall at 123 mm (4.9 in) across about 12 days. Interestingly, while September has a slightly higher humidity level at 71%, July's humidity is typically lower at 67%. For more details, you can view Portland weather in July.
In comparing the weather between August and September, we see a noticeable shift in temperature and humidity. August brings warmer conditions with an average temperature of 20°C (69°F), peaking at 28°C (82°F), while September cools down significantly, with an average of 17°C (63°F) and a maximum of 26°C (79°F). Additionally, September experiences slightly more precipitation at 77 mm (3.0 in) over 8 days compared to August's 75 mm (3.0 in) over 9 days. The humidity also rises in September to 71%, compared to August's 66%. For a closer look at the conditions in August, you can visit Portland weather in August.
In comparing the weather of September and October, we observe a notable shift in temperature and precipitation. September typically features milder conditions with an average temperature of 17°C (63°F) and a maximum of 26°C (79°F), while October sees a drop in average temperature to 12°C (54°F) with a maximum of only 21°C (71°F). Additionally, October experiences significantly more rainfall, with 163 mm (6.4 in) over 13 days compared to September's 77 mm (3.0 in) over 8 days. The humidity slightly increases from 71% in September to 78% in October, contributing to a more damp atmosphere. For a detailed overview of the weather conditions, you can visit Portland weather in October.
September and November present contrasting weather patterns. September typically enjoys milder temperatures, with averages around 17°C (63°F) and highs reaching 26°C (79°F), while humidity sits at a comfortable 71%. In contrast, November experiences a notable drop in temperature, averaging only 5°C (42°F) and reaching lows of -12°C (11°F). Moreover, November sees increased precipitation at 130 mm (5.1 in) over more days (12 days) compared to September's 77 mm (3.0 in) over 8 days. The humidity also rises in November to 84%, contributing to a much chillier and wetter atmosphere. For more insights, check out Portland weather in November.
September and December present a stark contrast in weather, reflecting the transition from late summer to mid-winter. In September, temperatures are generally mild, with an average of 17°C (63°F) and highs reaching up to 26°C (79°F). The month sees around 77 mm (3.0 in) of precipitation over about 8 days, while humidity hovers at a comfortable 71%. In contrast, December brings significantly colder conditions, with average temperatures plummeting to 0°C (33°F), and lows can drop as low as -18°C (-1°F). This winter month experiences more precipitation, totaling 144 mm (5.7 in) across approximately 10 days, and the humidity rises slightly to 81%. For more detailed information, you can check Portland weather in December.
In September, Portland transitions into a delightfully mild climate, marked by an average temperature that hovers around a comfortable 17°C (63°F). Although the month still enjoys the warmth of late summer, the cooler evenings hint at the approaching fall, with lows dipping to about 8°C (46°F). Precipitation also takes a more significant role, as 77 mm (3.0 in) falls over the course of the month, resulting in 8 rainy days. With humidity levels around 71%, the air feels crisp yet refreshing. This distinctive blend of warmth and coolness makes September a unique time in Portland, setting it apart from the hotter, drier summer months. For a deeper understanding of what to expect throughout the year, explore the full details of the Portland Climate.