September Weather in Porthmadog, United Kingdom

Last updated: March 17, 2025

In September, Porthmadog, United Kingdom, experiences a diverse range of weather conditions, making it an intriguing time for visitors. With a maximum temperature reaching 26°C (78°F) and an average of 14°C (57°F), the month offers warm days perfect for outdoor exploration. However, temperatures can dip as low as 6°C (42°F) during cooler nights. Expect considerable precipitation, with a total of 146 mm (5.7 in) spread over 18 days, contributing to the area's lush greenery. The humidity levels, averaging 85%, can create a refreshing coastal atmosphere, typical of this charming region. Whether you're gearing up for an adventure or seeking a peaceful retreat, September in Porthmadog presents a unique blend of scenic beauty and variable weather.

September Temperature in Porthmadog

In September, Porthmadog experiences a gentle transition as summer gracefully gives way to autumn. With temperatures ranging from a mild 6°C (42°F) at night to a warm 26°C (78°F) during the day, the month offers a comfortable average of 14°C (57°F). This is one of the year's warmest months, showcasing a significant rise from the earlier chill of spring and the lingering warmth of summer. The gradual cooling trend begins that will characterize the coming months, hinting at the cozy layers needed as October approaches. As evenings cool off, the vibrant hues of autumn start to paint the landscape, making September a delightful time to explore Porthmadog's stunning scenery.

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

The chart illustrates September temperature patterns in Porthmadog, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends.
JanFebMarAprMayJunJulAugSepOctNovDec424344475257605957524744
Data source: Temperature data for Porthmadog generated using information from the Copernicus Climate Change Service.
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The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Porthmadog

September in Porthmadog marks a noteworthy transition in the precipitation cycle, with 146 mm (5.7 in) of rain falling over an average of 18 days. This amount continues the trend of substantial rainfall observed throughout the summer, notably close to August's peak of 162 mm (6.4 in). However, as the year progresses into autumn, September's precipitation begins to taper off compared to October’s anticipated spike of 206 mm (8.1 in). The frequency of rainy days also reflects this seasonal shift, with September comfortably nestled in the middle range of days typically seen this year. As the landscape prepares for the onset of autumn, the steady rainfall in September serves as a reminder that Porthmadog's climate remains vibrant and rich, setting the stage for the next seasonal changes.

September Precipitation Trends in Porthmadog

The chart displays monthly precipitation patterns in Porthmadog, 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.
JanFebMarAprMayJunJulAugSepOctNovDec1211621526287106105162146206176203
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Porthmadog

As summer transitions to autumn, September in Porthmadog brings a noticeable rise in humidity, settling at 85%. This increase comes after the relatively lower levels experienced during the peak months of July and August, which hovered around 78% and 79% respectively. Following this slight uptick, the humidity reaches its peak in October at 90%. This trend is indicative of the gradual shift towards the wetter months, as the year progresses towards its end, with the humidity levels slowly climbing back toward the higher averages of winter, which average around 89% to 91%. Such fluctuations highlight the coastal town's maritime climate, where graceful transitions between seasons embody the rhythm of nature.

September Average Humidity in Porthmadog

This chart illustrates the average monthly humidity levels in Porthmadog, 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.
JanFebMarAprMayJunJulAugSepOctNovDec89%88%86%85%79%81%78%79%85%90%91%89%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Porthmadog

As summer fades into autumn, September in Porthmadog, United Kingdom, sees a UV Index of 5, indicating a moderate level of sun exposure. This marks a gradual decline from the peak 8 observed in July and June, where sun protection became crucial with a burn time of just 15 minutes. In September, residents and visitors can enjoy an extended burn time of 30 minutes, making it a great time to bask in the outdoors while still being mindful of the sun. The trend throughout the month reflects a shift from the high summer indices, allowing a more comfortable outdoor experience without the intense risk of sunburn typical of the earlier months. For more details on UV levels throughout the year, check out the full Porthmadog UV Index.

Maximum UV Index Levels in Porthmadog for September

The chart shows the monthly maximum UV Index (UVI) for Porthmadog 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.
JanFebMarAprMayJunJulAugSepOctNovDec124578875421
Data source: Porthmadog 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 Porthmadog

September in Porthmadog, United Kingdom, sees a delightful transition as summer gently fades into autumn. With 315 hours of sunshine, it's a significant drop from the vibrant 421 hours in July and 383 hours in August, yet it remains a splendid time to enjoy the outdoors. The month captures a charming balance, where lingering warmth meets the crispness of fall, inviting both locals and visitors to explore the scenic beauty of the region. As daylight hours gradually decrease, September offers a golden glow to adventures, making it a perfect backdrop for memorable experiences before the chilly October sets in.

Monthly Sunshine Duration in Porthmadog: September Highlighted

The September sunshine duration represents the total number of hours Porthmadog 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.
JanFebMarAprMayJunJulAugSepOctNovDec93h162h228h335h415h404h421h383h315h238h126h109h
Data source: Porthmadog September Sunshine duration data generated using information from the Copernicus Climate Change Service.

Chance of Sun in Porthmadog During September

In Porthmadog, September experiences a 22% chance of sunny weather, which positions it among the relatively milder months for sunshine compared to the rest of the year. Following the vibrant days of April, when the sun graces the town 46% of the time, the likelihood dwindles as summer transitions into autumn. Interestingly, September's sunshine probability is similar to that of January and November, suggesting a seasonal trend where the promise of sun starts to diminish as the year progresses. Despite its modest chance of clear skies, September still holds the charm of late summer, making it a time for visitors to enjoy the lingering warmth before the cooler months set in.

Percentage of Sunny Days in September in Porthmadog

The chart illustrates the percentage of sunny days in Porthmadog 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 Porthmadog experiences clear skies throughout the year.
JanFebMarAprMayJunJulAugSepOctNovDec20%22%25%46%30%27%36%25%22%16%20%20%
Data source: Porthmadog September chance of sun data, generated using information from the Copernicus Climate Change Service.

Daylight Hours in Porthmadog in September

As summer fades into autumn, September in Porthmadog, United Kingdom, brings a gentle decline in daylight duration, offering approximately 12 hours of sunlight each day. This marks a shift from the vibrant 16 hours of daylight seen in June and July, gradually making way for the shorter days of fall. Following the lengthy and sunlit summer months, September embodies a transitional phase—where daylight begins to wane, yet the days remain comfortably long, offering ample time for outdoor adventures and enjoying the stunning landscapes. As this month draws to a close, the lingering warmth of late summer still invites exploration before the shorter days of October settle in with just 10 hours of light.

Average Daylight Hours in Porthmadog for September

The chart illustrates the variation in daylight duration in Porthmadog throughout the year, with September highlighted. It shows the monthly changes in daylight hours, calculated by summing the hours between sunrise and sunset.
JanFebMarAprMayJunJulAugSepOctNovDec8h 10m9h 51m11h 54m14h15h 51m16h 50m16h 18m14h 38m12h 36m10h 31m8h 38m7h 37m
Data source: Porthmadog daylight hours, calculated by summing the hours between sunrise and sunset for each day.

September Winds in Porthmadog

As September rolls in, Porthmadog experiences a gentle shift in its wind conditions, with average wind speeds reaching 3.7 m/s (8 mph). This marks a notable decrease compared to the brisk breezes of the preceding summer months, where winds hovered around 4.4 m/s in August. The trend of declining wind speeds continues into early autumn, suggesting a serene transition as the vibrant energy of summer slowly ebbs away. With October anticipated to revive the gales at 6.4 m/s (14 mph), September remains a tranquil interlude, perfect for enjoying the calming beauty of the coastal landscape.

Average September Wind Speed in Porthmadog

The chart displays monthly wind speed patterns in Porthmadog, 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.
JanFebMarAprMayJunJulAugSepOctNovDec5.36.65.73.84.74.03.24.43.7 m/s6.45.55.9
Data source: Porthmadog September wind data, generated using information from the Copernicus Climate Change Service.

How September Weather in Porthmadog Compares to Other Months

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

In September, the weather tends to be much milder with average temperatures ranging from 6°C (42°F) to a warm maximum of 26°C (78°F), while January presents a stark contrast with cooler temperatures averaging between -1°C (30°F) and 13°C (55°F). Despite September having more days of precipitation at 18 days, the total rainfall is slightly higher at 146 mm (5.7 in), compared to January’s 121 mm (4.8 in) over 16 days. Humidity remains relatively high in both months, reaching 85% in September and slightly increasing to 89% in January. For a detailed look at the January weather in Porthmadog, you can check Porthmadog weather in January.

September and February present contrasting weather patterns. September typically enjoys a milder climate, with temperatures ranging from a minimum of 6°C (42°F) to an average of 14°C (57°F) and a maximum of 26°C (78°F). In contrast, February is much colder, where temperatures can drop to a minimum of -3°C (28°F) and reach an average of 6°C (43°F), peaking at 15°C (60°F). Both months experience significant precipitation, with September receiving 146 mm (5.7 in) over 18 days and February slightly wetter at 162 mm (6.4 in) over 19 days. Additionally, February has a higher humidity level at 88%, compared to September’s 85%. For more details on the weather during this chilly month, you can check out Porthmadog weather in February.

When comparing the weather in September and March, notable differences arise. September typically enjoys milder temperatures, ranging from a minimum of 6°C (42°F) to a maximum of 26°C (78°F), with an average of 14°C (57°F). In contrast, March experiences cooler temperatures, with a minimum of -5°C (23°F) and a maximum of 16°C (61°F), yielding an average of only 7°C (44°F). Both months see significant precipitation—September records 146 mm (5.7 in) over 18 days, while March has slightly higher precipitation levels at 152 mm (6.0 in) across 19 days. Moreover, humidity is quite similar, with September at 85% and March at 86%. For more detailed information about the weather during this month, you can check Porthmadog weather in March.

When comparing the weather in September and April, it's evident that September tends to be warmer and wetter. In September, temperatures range from a minimum of 6°C (42°F) to a maximum of 26°C (78°F), with an average of 14°C (57°F). The month experiences a significant amount of rainfall, totaling 146 mm (5.7 in) over 18 days, maintaining a high humidity level of 85%. In contrast, April sees cooler temperatures, with a minimum of 0°C (33°F) and a maximum of 19°C (66°F), averaging just 8°C (47°F). Precipitation is much lower at 62 mm (2.4 in) spread over 12 days, with slightly reduced humidity at 84%. For specific details on the weather during this month, you can visit Porthmadog weather in April.

When comparing the weather between September and May, September tends to be warmer overall, with average temperatures reaching up to 14°C (57°F) compared to May's average of 11°C (52°F). September also has a higher maximum temperature of 26°C (78°F), while May peaks at 23°C (73°F). However, September is significantly wetter, with 146 mm (5.7 in) of precipitation over 18 days, whereas May sees only 87 mm (3.4 in) of rain across 12 days. Humidity levels are higher in September at 85% compared to 79% in May. For more specific insights about the weather in May, you can check Porthmadog weather in May.

When comparing the weather in September to that of June, both months showcase similar average temperatures, hovering around 14°C (57°F). However, September tends to experience slightly cooler nights, with minimum temperatures dipping to 6°C (42°F) compared to June's minimum of 7°C (46°F). In terms of precipitation, September is wetter, receiving 146 mm (5.7 in) over 18 days, while June has a more moderate 106 mm (4.2 in) over just 16 days. Additionally, September has a higher humidity level at 85%, compared to June's 81%. For further details on June weather, you can check this link: Porthmadog weather in June.

September weather in Porthmadog is characterized by slightly cooler temperatures, with a minimum of 6°C (42°F) and an average of 14°C (57°F), compared to July's minimum of 9°C (48°F) and an average of 15°C (60°F). While July experiences a maximum temperature of 25°C (77°F), September peaks at a warmer 26°C (78°F). Precipitation is more prevalent in September, accumulating to 146 mm (5.7 in) over 18 days, while July sees 105 mm (4.1 in) across 15 days. Additionally, the humidity in September is higher at 85%, compared to July's 78%. For more detailed information, check out Porthmadog weather in July.

In comparison to August, September showcases slightly cooler temperatures, with minimums dipping to 6°C (42°F) and averaging around 14°C (57°F), while August records a minimum of 9°C (49°F) and an average of 15°C (60°F). September also sees a higher maximum temperature of 26°C (78°F), compared to August's peak of 24°C (75°F). However, September experiences greater precipitation, with 146 mm (5.7 in) over 18 days, while August has a total of 162 mm (6.4 in) spread across 22 days. Humidity levels are relatively higher in September at 85%, compared to 79% in August. For more detailed insights, check Porthmadog weather in August.

September and October present notable changes in weather conditions. In September, temperatures range from a minimum of 6°C (42°F) to a maximum of 26°C (78°F), with an average of 14°C (57°F). The month sees about 146 mm (5.7 in) of precipitation spread over 18 days, accompanied by a humidity level of 85%. In contrast, October experiences cooler temperatures with a minimum of 1°C (33°F) and a maximum of 20°C (68°F), averaging at 11°C (53°F). Precipitation increases to 206 mm (8.1 in) over 22 days, and humidity rises slightly to 90%. For more detailed weather insights, you can check Porthmadog weather in October.

In September, the weather is generally milder, with average temperatures ranging from a minimum of 6°C (42°F) to a maximum of 26°C (78°F), and an average temperature of 14°C (57°F). The month experiences considerable rainfall of 146 mm (5.7 in) over 18 days, resulting in a humidity level of 85%. In contrast, November brings cooler temperatures, with a range of 1°C (34°F) to 14°C (58°F) and an average temperature of only 8°C (48°F). The precipitation also increases to 176 mm (6.9 in), occurring over 21 days, accompanied by a higher humidity of 91%. For a detailed look at the conditions, you can check out Porthmadog weather in November.

In Porthmadog, September brings mild temperatures, with a minimum of 6°C (42°F) and an average of 14°C (57°F), peaking at 26°C (78°F). The weather is relatively humid at 85%, and precipitation is common, averaging 146 mm (5.7 in) over 18 rainy days. In contrast, December sees a significant drop in temperatures, with minimums reaching -2°C (29°F) and an average of 7°C (45°F), while the maximum rarely exceeds 12°C (54°F). The month is wetter, with 203 mm (8.0 in) of rain falling over 24 days, and humidity intensifies to 89%. For more detailed information, you can visit Porthmadog weather in December.

Compare Porthmadog's Climate with Cities Worldwide

Conclusion: What to Expect From September Weather in Porthmadog

September in Porthmadog brings a noticeable transition as summer wanes, with temperatures averaging a mild 14°C while occasionally peaking at a comfortable 26°C. Unlike the drier summer months, this period experiences increased rainfall, with 18 days of precipitation contributing to a total of 146 mm for the month. The humidity levels also remain high at around 85%, making the air feel more saturated. This blend of mild temperatures and frequent rain sets September apart, leading to a fresh and lush environment perfect for enjoying the natural beauty of the region. For more detailed insights, check out Porthmadog Climate.