September Weather in Castletown, Isle of Man

Last updated: August 21, 2025

In September, Castletown on the Isle of Man experiences a mild maritime climate, with maximum temperatures reaching 19°C (67°F) and averaging about 14°C (58°F). Visitors can expect a cozy atmosphere as minimum temperatures typically hover around 10°C (51°F). The month is characterized by significant rainfall, with 91 mm (3.6 in) spread over 14 days, contributing to a high humidity level of 85%. This blend of warmth and moisture creates a lush landscape, making September an appealing time to explore the scenic beauty of Castletown, albeit with a chance of occasional showers.

September Temperature in Castletown

As summer gently fades into autumn, Castletown on the Isle of Man experiences a pleasant shift in temperatures during September. With minimums around 10°C (51°F) and maximums peaking at 19°C (67°F), the weather remains quite mild, making it a perfect time for outdoor activities. The average temperature hovers at a comfortable 14°C (58°F), signaling the gradual transition from the warmer summer months, where temperatures frequently reached the mid-teens. This month serves as a bridge, gently ushering in the cooler tones of autumn while still basking in the remnants of summer warmth. It's an ideal time for exploring the scenic beauty of Castletown before the more brisk months set in.

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

The chart illustrates September temperature patterns in Castletown, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Castletown, September typically has an average temperature of {2}°C ({3}°F), with highs reaching up to {4}°C ({5}°F) and lows dropping to around {6}°C ({7}°F).
JanFebMarAprMayJunJulAugSepOctNovDec464545475155585958555047
Data source: Temperature data for Castletown 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 Castletown

September in Castletown, Isle of Man, showcases a noteworthy blend of wet and dry as 91 mm (3.6 in) of precipitation punctuates the month across 14 days. This volume reflects a slight dip from the wetter months of August and October, hinting at the onset of autumnal transitions. The rainfall in September remains substantial, aligning closely with the summer's averages while setting the stage for the upcoming peak months in terms of precipitation. As the days grow shorter, the consistency of rainfall suggests a comforting rhythm in the island's cycle, reminding residents that change is both inevitable and refreshing.

September Precipitation Trends in Castletown

The chart displays monthly precipitation patterns in Castletown, 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. In Castletown, September typically receives around {2} mm ({3} inches) of precipitation spread over approximately {4} days.
JanFebMarAprMayJunJulAugSepOctNovDec8110687364470709492142144144
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Castletown

In September, Castletown, Isle of Man experiences a notable shift as humidity levels rise to 85%, signaling the transition from summer to autumn. This moderate increase contrasts with the drier summer months of July and August, which recorded 78% and 79% respectively. As the year progresses towards its wetter months, humidity steadily climbs, peaking again at 90% in October and 91% in November. This trend highlights the region’s characteristic moisture-laden atmosphere, emphasizing the lush, verdant landscapes that define the Isle of Man as the seasons change.

September Average Humidity in Castletown

This chart illustrates the average monthly humidity levels in Castletown, with September’s data highlighted for easy comparison. It shows the fluctuation in humidity throughout the year, helping you understand how conditions vary by season. In September, average humidity in Castletown is approximately {2}%, offering insight into how humid the weather typically is during this month.
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 Castletown

As we transition into September in Castletown, Isle of Man, the UV Index settles at 5, marking a return to the moderate exposure category that mirrors the levels seen in both April and October. This slight decline from the previous months indicates a shift in the season, as the sun’s strength wanes after the high summer peaks of 8. With a burn time of 30 minutes, it's essential to remain mindful of sun exposure. This change not only highlights the fluctuating nature of UV levels throughout the year but also serves as a reminder to enjoy the outdoors safely. For more insights on UV conditions in Castletown, visit Castletown UV Index.

Maximum UV Index Levels in Castletown for September

The chart shows the monthly maximum UV Index (UVI) for Castletown 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. In September, the maximum UV index in Castletown typically reaches {2}, which falls under the {3} exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec123578875321
Data source: Castletown 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 Castletown

September in Castletown, Isle of Man, brings a delightful transition as summer lingers with 314 hours of sunshine. This marks a noteworthy decline from the sun-soaked peak of May and July, both basking in 418 hours, yet it still maintains a vibrant glow compared to the chillier months that follow. As autumn approaches, the warmth of sun-drenched days gives way to a cozy ambiance, beautifully mirroring the gradually diminishing daylight seen from April's 341 hours to October’s diminishing 244 hours. With each sunset, the charm of September shines on, reminding visitors of the fleeting beauty before winter's embrace.

Monthly Sunshine Duration in Castletown: September Highlighted

The September sunshine duration represents the total number of hours Castletown 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.
JanFebMarAprMayJunJulAugSepOctNovDec90h161h233h341h418h411h418h376h314h244h131h104h
Data source: Castletown September Sunshine duration data generated using information from the Copernicus Climate Change Service.

Chance of Sun in Castletown During September

As we transition into September in Castletown, Isle of Man, the likelihood of enjoying sunny weather takes a dip, with only a 24% chance of sunshine. This decline follows a somewhat unpredictable summer, where the chances hovered around 29% in August and 40% in July. Notably, the peak for sunny days occurs in April at 52%, suggesting that while the warmth of summer may linger, the brightness of early spring still reigns supreme. As autumn creeps in, the chances continue to decline, reaching a low of 21% by December. Thus, if you're hoping for sun-soaked September days, it's wise to manage expectations and perhaps make alternative plans for those inevitable gray skies.

Percentage of Sunny Days in September in Castletown

The chart illustrates the percentage of sunny days in Castletown 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 Castletown experiences clear skies throughout the year.
JanFebMarAprMayJunJulAugSepOctNovDec28%26%25%52%40%29%40%29%24%22%22%21%
Data source: Castletown September chance of sun data, generated using information from the Copernicus Climate Change Service.

Daylight Hours in Castletown in September

As summer fades into autumn in Castletown, Isle of Man, September brings a gentle transition in daylight, with an average of 12 hours illuminating the days. This marks a noticeable step down from the sun-drenched heights of June and July, where daylight peaked at a generous 17 hours. The gradual decline reflects the seasonal shift, starting from May's vibrant 16 hours, and tapering off through August's 14 hours. As the days grow shorter, September stands as a bridge, combining elements of summer's brightness with the approaching coziness of autumn, hinting at the 10 hours that await in October. This rhythmic ebb and flow of daylight not only signals changing seasons but also invites residents and visitors alike to savor the unique beauty of late summer sunsets.

Average Daylight Hours in Castletown for September

The chart illustrates the variation in daylight duration in Castletown throughout the year, with September highlighted. It shows the monthly changes in daylight hours, calculated by summing the hours between sunrise and sunset.
JanFebMarAprMayJunJulAugSepOctNovDec8h9h 46m11h 54m14h 5m16h 1m17h 2m16h 29m14h 45m12h 38m10h 28m8h 30m7h 26m
Data source: Castletown daylight hours, calculated by summing the hours between sunrise and sunset for each day.

September Winds in Castletown

As the summer fades into autumn, September in Castletown, Isle of Man enjoys a gentle breeze, with an average wind speed of 6.0 m/s (13 mph). This marks a slight uptick from the calmer summer months, where July recorded the lowest winds at 4.3 m/s (10 mph). While the winds are still relatively mild compared to the invigorating gusts of winter, which see an increase to 9.3 m/s (21 mph) in October and November, September serves as a gentle transition. This month strikes a harmonious balance, providing a refreshing quality to the air while still retaining the warmth of summer, enticing both locals and visitors to embrace the changing season.

Average September Wind Speed in Castletown

The chart displays monthly wind speed patterns in Castletown, 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.
JanFebMarAprMayJunJulAugSepOctNovDec8.510.58.55.86.46.64.35.76.0 m/s9.39.39.1
Data source: Castletown September wind data, generated using information from the Copernicus Climate Change Service.

How September Weather in Castletown Compares to Other Months

Weather in Castletown varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Castletown, focusing on differences in temperature, rainfall, humidity, and UV levels.

In September, temperatures in Castletown average around 14°C (58°F), with a comfortable range from a minimum of 10°C (51°F) to a maximum of 19°C (67°F). The month experiences a fair amount of rainfall, totaling 91 mm (3.6 in) across 14 days, accompanied by relatively high humidity at 85%. In contrast, January sees cooler temperatures, with averages dipping to 8°C (46°F) and ranging from a minimum of 3°C (38°F) to a maximum of 13°C (56°F). Although the precipitation is slightly lower at 81 mm (3.2 in) over the same number of rainy days, humidity rises to 89%, contributing to a colder and damp atmosphere. For more detailed insights, check out Castletown weather in January.

September and February present quite different weather experiences. September enjoys milder temperatures, with average highs around 19°C (67°F) and relatively warmer evenings, while February is much cooler, with average highs only reaching 12°C (54°F). Additionally, February tends to be wetter, receiving an average of 106 mm (4.2 in) of precipitation over 18 days, compared to September's 91 mm (3.6 in) over 14 days. Humidity is slightly higher in February at 88%, compared to September's 85%. For more detailed information, you can check Castletown weather in February.

When comparing the weather in September and March, it's clear that the two months offer distinctly different climates. September tends to be milder, with temperatures ranging from a minimum of 10°C (51°F) to a maximum of 19°C (67°F) and an average of 14°C (58°F). In contrast, March experiences cooler temperatures, with a minimum of -1°C (30°F), an average of 7°C (45°F), and a maximum of 11°C (52°F). Precipitation is similar in both months, with September receiving 91 mm (3.6 in) over 14 days, while March has slightly less at 87 mm (3.4 in) but over more days, totaling 18. Despite these similarities in rainfall, the humidity levels remain comparable, with September at 85% and March slightly higher at 86%. For more insights, you can check the detailed statistics here: Castletown weather in March.

When comparing the weather between September and April, it’s evident that September enjoys milder temperatures, with averages around 14°C (58°F) and maximums reaching up to 19°C (67°F). In contrast, April tends to be cooler, with average temperatures around 8°C (47°F) and maximums not exceeding 13°C (56°F). While September sees more precipitation, totaling 91 mm (3.6 in) over approximately 14 days, April experiences significantly less with 36 mm (1.4 in) across about 8 days. Additionally, both months feature high humidity levels, though September is slightly more humid at 85% compared to April's 84%. For a detailed look at April weather specifics, you can visit Castletown weather in April.

When comparing the weather in September and May, September tends to be slightly warmer, with average temperatures ranging from a minimum of 10°C (51°F) to a maximum of 19°C (67°F), while May sees lower averages, with minimum temperatures around 5°C (42°F) and maximum temperatures reaching 16°C (60°F). Additionally, September experiences more rainfall, with 91 mm (3.6 in) over 14 days, compared to May's 44 mm (1.7 in) spread over 9 days. The humidity during September is also higher at 85%, compared to May's 79%, contributing to a more humid feel late in the summer season. For those interested in the specifics of May weather, you can find more details here: Castletown weather in May.

When comparing the weather in September and June, September tends to be slightly warmer with average temperatures reaching 14°C (58°F) and maximums of 19°C (67°F), compared to June's average of 13°C (55°F) and maximum of 17°C (64°F). September also experiences more rainfall, with a total precipitation of 91 mm (3.6 in) over 14 days, whereas June sees 70 mm (2.8 in) spread across 11 days. The humidity is marginally higher in September at 85%, compared to June's 81%. For more detailed information, you can check Castletown weather in June.

September weather shows slightly cooler temperatures compared to July, with a minimum of 10°C and a maximum of 19°C, while July maintains a minimum of 12°C and the same maximum. Both months average 14°C, but September experiences more precipitation at 91 mm over 14 days, compared to July's 70 mm over 12 days. Additionally, the humidity levels in September are higher at 85% compared to July’s 78%. For more detailed information on July weather patterns, you can check Castletown weather in July.

In comparing the weather of September to that of August, one can note a slight drop in temperature. September sees minimum temperatures of 10°C (51°F) and an average of 14°C (58°F), while August offers slightly warmer conditions with a minimum of 12°C (54°F) and an average of 15°C (59°F). August also boasts a marginally lower maximum temperature of 18°C (65°F) compared to September's 19°C (67°F). Precipitation levels are quite similar, with September recording 91 mm (3.6 in) over 14 days and August at 94 mm (3.7 in) over 15 days. Additionally, September's humidity is higher at 85%, compared to 79% in August. For more detailed insights, you can check Castletown weather in August.

September and October showcase a gradual transition in weather conditions. In September, temperatures range from a minimum of 10°C (51°F) to a maximum of 19°C (67°F), with an average of 14°C (58°F). Rainfall occurs on about 14 days, accumulating to 91 mm (3.6 in) of precipitation, while humidity remains high at 85%.

Conversely, October sees a further drop in temperatures, with a minimum of 7°C (45°F) and a maximum of 17°C (63°F), averaging 13°C (55°F). The month is notably wetter, recording 142 mm (5.6 in) of rain over 18 days, and humidity increases slightly to 90%. For a detailed look at October weather in Castletown, visit Castletown weather in October.

September generally offers milder weather compared to November, with average temperatures peaking at around 14°C (58°F) and highs reaching 19°C (67°F). In contrast, November sees cooler temperatures, with averages dropping to 10°C (51°F) and maximums only hitting 14°C (58°F). Additionally, November experiences increased precipitation, totaling 143 mm (5.6 in) over 20 days, compared to September's 91 mm (3.6 in) over 14 days. The humidity also rises slightly in November, reaching 91%, compared to 85% in September. For a detailed look at November weather, you can check Castletown weather in November.

In comparing September and December weather, it’s clear that December is significantly cooler, with average temperatures dropping from 14°C (58°F) in September to just 9°C (48°F). While both months see a fair amount of precipitation, December has higher rainfall at 144 mm (5.7 in) compared to September's 91 mm (3.6 in), and experiences more rainy days—22 in December versus 14 in September. Humidity levels also rise slightly in December, reaching 89%, compared to 85% in September. For more detailed information, you can visit Castletown weather in December.

Compare Castletown's Climate with Cities Worldwide

Conclusion: What to Expect From September Weather in Castletown

As the summer days fade, September in Castletown offers a unique blend of cooler temperatures and increased precipitation, setting it apart from the warmer months. With an average temperature of 14°C (58°F) and a significant 91 mm (3.6 in) of rain over 14 days, the transition to autumn becomes palpable. Humidity levels rise to 85%, creating an atmospheric feel that contrasts sharply with the drier summer air. Whether you're enjoying the crisp mornings or the occasional rainfall, this month invites both locals and visitors to embrace the beauty of change. For more insights into weather patterns throughout the year, check out Castletown Climate.