Last updated: March 17, 2025
September in Portsmouth, United Kingdom brings a delightful mix of mild temperatures and occasional rainfall, making it a charming time to explore the coast. With daytime highs averaging around 24°C (76°F) and cooler nights dropping to a pleasant 8°C (47°F), the weather is ideal for outdoor activities. While the month sees 57 mm (2.2 in) of rain over about 10 days, the 82% humidity adds a refreshing touch to the brisk sea air. This transitional month marks the shift from summer warmth to the cozy embrace of autumn, inviting both locals and visitors to enjoy the scenic beauty of the region.
As summer transitions into autumn, September in Portsmouth showcases a delightful shift in temperatures. The month begins with a comfortable average of 16°C (61°F), peaking at a pleasant 24°C (76°F), reflecting a lingering warmth reminiscent of summer. Nights cool down to a mild 8°C (47°F), making evenings ideal for strolls along the waterfront. This gradual decline in temperatures signals the end of the warmer months, but the weather remains inviting for outdoor activities and late-season excursions. Overall, September strikes a lovely balance, offering a taste of fall while still holding onto the warmth of summer’s embrace.
September in Portsmouth sees a moderate precipitation level of 57 mm (2.2 in), making it a relatively wet month in comparison to the preceding summer months. With rainfall occurring on 10 days, this slight uptick in precipitation prepares the city for the wetter autumn season ahead. Notably, September's rainfall is less than August's 78 mm (3.1 in), highlighting a trend of diminishing summer rains as the year transitions into cooler months. This pattern sets the stage for October, which typically witnesses a significant increase in precipitation, often exceeding 100 mm. Overall, September acts as a bridge between the relatively dry summer and the more rain-soaked conditions of fall.
In September, Portsmouth experiences a notable shift in humidity, averaging around 82%. This increase marks a transition from the dryer summer months of July and August, which see humidity levels plummet to 71% and 76%, respectively. As autumn approaches, the air becomes steadily more saturated, reminiscent of the winter months ahead where humidity peaks at 90% in October, followed by a consistent rise to 92% in both November and December. Overall, September presents a balanced yet moist atmosphere, bridging the gap between the warmth of summer and the cooler, wetter months that follow.
As September rolls in, Portsmouth sees a UV Index of 6, categorizing the sun exposure as high. While the warmer months of May through August showcase peak UV levels, September marks a slight decrease, yet still necessitates caution. With a burn time of about 25 minutes, it's crucial to stay protected during outdoor activities. As autumn approaches, this month serves as a reminder to enjoy the sunny days while being mindful of UV safety. For more detailed insights, check the Portsmouth UV Index.
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September in Portsmouth, United Kingdom, offers a delightful transition from the sun-drenched summer months to the crisper autumn days. With an impressive 320 hours of sunshine, it stands as a serene pause following the radiant July, which boasts the highest sunlight hours of the year at 423. While September may see a notable decrease in sunlight compared to the peak summer, it still outshines the beginning of the year, significantly eclipsing the meager hours of January. The weather this month invites both locals and visitors to relish in the golden hues of early fall, making it a perfect time to enjoy outdoor activities before the days grow shorter and more overcast. Overall, September beautifully encapsulates the lingering warmth of summer while gently ushering in the autumn chill.
In September, Portsmouth experiences a 36% chance of sunny weather, reflecting a shift in climate as summer transitions to autumn. This figure indicates a slight increase from the drier summer months of July and August, where the chances of sunshine were 42% and 33%, respectively. Interestingly, September stands out with a greater likelihood of sun compared to the chillier months that follow, such as October at 30%. As the days gradually shorten, this month offers a delightful opportunity to enjoy lingering warmth and those precious sunny moments before autumn fully sets in. Thus, while September may not guarantee sunshine, it presents a pleasantly moderate chance that invites outdoor exploration.
In September, Portsmouth experiences a transition from the vibrant summer days to the softer light of autumn, with approximately 12 hours of daylight. This month marks a gentle decline from the long, sun-filled days of summer, where June boasted a peak of 16 hours. Following the height of summer, daylight gradually diminishes, with September still offering a generous amount of sunlight compared to the approaching winter months. As the year progresses, daylight tapers down to 10 hours in October and further to a mere 8 hours by November. This rhythmic ebb and flow of daylight highlights the changing seasons, creating a unique atmosphere that blends the lingering warmth of summer with the crispness of the autumn air.
As summer gives way to autumn, September in Portsmouth brings a gentle shift in the breeze, with average wind speeds settling at 4.8 m/s (11 mph). This marks a notable decrease from the bustling winds of February and May, which both see higher averages of 6.9 m/s (16 mph) and 6.1 m/s (14 mph), respectively. The mellow September winds create a serene atmosphere, making it an ideal time for long walks along the coast or enjoying outdoor cafés. As the month progresses, the winds typically begin to pick up again in October, hinting at the seasonal transition that lies ahead. Overall, September’s breezy yet calm conditions signify a tranquil punctuation before Portsmouth braces for the gustier months to come.
The weather in Portsmouth 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 Portsmouth and find detailed weather information for every month.
In September, the weather in Portsmouth is generally milder, with average temperatures ranging from a minimum of 8°C (47°F) to a maximum of 24°C (76°F), and an average of 16°C (61°F). September experiences about 57 mm (2.2 in) of rainfall over roughly 10 days, accompanied by a humidity level of 82%. In contrast, January brings cooler conditions, with temperatures ranging from a minimum of 0°C (32°F) to a maximum of 13°C (56°F), averaging just 7°C (44°F). This month sees slightly higher precipitation at 68 mm (2.7 in) over 11 days, along with a higher humidity level of 91%. For a more detailed look at January's climate, check out Portsmouth weather in January.
September and February present contrasting weather patterns. September typically enjoys milder temperatures, with a minimum of 8°C (47°F) and an average of 16°C (61°F), peaking at 24°C (76°F). The month experiences about 57 mm (2.2 in) of precipitation spread over 10 days, with humidity levels around 82%. In stark contrast, February is much colder, featuring minimum temperatures of -3°C (28°F) and an average of 7°C (45°F), climbing to a maximum of only 13°C (55°F). This winter month sees increased rainfall as well, totaling approximately 75 mm (3.0 in) over about 12 days, accompanied by higher humidity at 89%. For a more detailed look at February weather, check out Portsmouth weather in February.
In September, the weather is milder with average temperatures ranging from a minimum of 8°C (47°F) to a maximum of 24°C (76°F), making it a pleasant time for outdoor activities. In contrast, March experiences cooler temperatures, with averages between -3°C (28°F) and 14°C (58°F), indicating a seasonal shift as winter transitions to spring. While September sees around 57 mm (2.2 in) of precipitation over approximately 10 days, March is slightly wetter, with 70 mm (2.7 in) of rain spread across 13 days. Additionally, the humidity levels are higher in March at 86%, compared to September's 82%. For more details on March weather, you can visit Portsmouth weather in March.
In comparing the weather between September and April, September generally offers milder temperatures, with an average of 16°C (61°F) and maximums reaching up to 24°C (76°F). In contrast, April typically sees cooler conditions, with an average temperature of 10°C (50°F) and maximums peaking at 19°C (66°F). While both months experience a fair amount of precipitation, September has slightly higher rainfall at 57 mm (2.2 in) over about 10 days, compared to April's 32 mm (1.3 in) over 7 days. Additionally, humidity levels are comparable, with September at 82% and April slightly higher at 85%. For more detailed information on how weather conditions unfold during this month, you can check Portsmouth weather in April.
In September, the weather tends to be warmer than in May, with average temperatures reaching up to 16°C (61°F) and maximums of 24°C (76°F). In contrast, May has a cooler average temperature of 13°C (55°F) and a maximum of 22°C (71°F). Both months experience similar precipitation levels, with September receiving 57 mm (2.2 in) over about 10 days and May slightly less at 56 mm (2.2 in) over 11 days. Humidity is also slightly higher in September at 82%, compared to 79% in May. For more detailed information, you can check Portsmouth weather in May.
In comparing the weather of September and June, both months exhibit similar average temperatures, hovering around 16°C (61°F). However, September experiences slightly cooler minimum and maximum temperatures, with values ranging from 8°C (47°F) to 24°C (76°F), compared to June's range of 9°C (49°F) to 25°C (76°F). Precipitation is more prevalent in June, with a total of 73 mm (2.9 in) over 9 days, while September sees 57 mm (2.2 in) over 10 days. Humidity levels are comparable, at 82% in September and 80% in June, contributing to the similar feel of the two months. For more detailed information, you can check Portsmouth weather in June.
In comparing the weather of September to July, we see a noticeable shift in temperature and humidity. September tends to be cooler, with an average temperature of 16°C (61°F) and a minimum of 8°C (47°F), while July is warmer with an average of 18°C (65°F) and a minimum of 12°C (53°F). Additionally, July experiences slightly less precipitation, recording 58 mm (2.3 in) over 11 days compared to September’s 57 mm (2.2 in) spread across 10 days. Humidity is also higher in September at 82%, compared to 71% in July. For a more detailed look at July weather, you can check out Portsmouth weather in July.
September weather tends to be cooler and slightly wetter compared to August. In September, temperatures range from a minimum of 8°C (47°F) to a maximum of 24°C (76°F), with an average of 16°C (61°F), while August boasts milder temperatures with a minimum of 11°C (52°F) and a maximum of 26°C (80°F), averaging 18°C (64°F). Precipitation is also more prevalent in August, with 78 mm (3.1 in) over 12 days, compared to September's 57 mm (2.2 in) across 10 days. Additionally, September experiences higher humidity at 82%, whereas August has a slightly lower humidity level of 76%. For a closer look at the weather specifics, check out Portsmouth weather in August.
September and October present a notable transition in weather patterns. In September, temperatures range from a minimum of 8°C (47°F) to a maximum of 24°C (76°F), with an average of 16°C (61°F). The month experiences about 57 mm (2.2 in) of precipitation over 10 days, accompanied by a relatively comfortable humidity level of 82%. In contrast, October brings cooler temperatures, with a minimum of 4°C (40°F), an average of 13°C (56°F), and a maximum of 20°C (68°F). This month sees an increase in precipitation, totaling 117 mm (4.6 in) over 16 days, and the humidity rises to 90%. For a more detailed look at October's climate, you can check Portsmouth weather in October.
September typically offers milder weather compared to November, with temperatures ranging from a minimum of 8°C (47°F) to a maximum of 24°C (76°F) and an average of 16°C (61°F). The month experiences around 57 mm (2.2 in) of precipitation over about 10 days, with humidity levels at 82%. In contrast, November sees a significant drop in temperatures, with a minimum of 1°C (33°F) and an average of 10°C (50°F), peaking at 16°C (61°F). This month is also wetter, receiving approximately 87 mm (3.4 in) of rainfall across 15 days, and the humidity rises to 92%. For more details on November conditions, you can check Portsmouth weather in November.
In September, the weather typically features milder temperatures, with a minimum of 8°C (47°F) and an average of 16°C (61°F), reaching highs of 24°C (76°F). The month sees about 57 mm (2.2 in) of precipitation over approximately 10 days, along with a humidity level of 82%. In contrast, December experiences much cooler conditions, with temperatures dropping to a minimum of 0°C (33°F), an average of 8°C (47°F), and a maximum of just 14°C (57°F). The month is also wetter, with precipitation totaling 118 mm (4.7 in) over around 16 days, accompanied by higher humidity at 92%. For more detailed insights, you can check Portsmouth weather in December.
As September rolls in, Portsmouth experiences a notable transition in weather, offering a delightful blend of mild temperatures and higher humidity. With an average temperature hovering around 16°C (61°F), the early fall days feel significantly cooler compared to the summer's warmth. However, the occasional peaks of 24°C (76°F) still allow for pleasant outings. Rainfall becomes more frequent, with 10 days of precipitation, adding a hint of unpredictability to the month. This blend of conditions makes September a unique time in Portsmouth, as the vibrant summer fades into the cozy embrace of autumn. For more on the city's weather patterns throughout the year, visit Portsmouth Climate.