September Weather in Dun Laoghaire, Ireland

Last updated: March 17, 2025

September in Dun Laoghaire, Ireland, showcases a blend of mild temperatures and frequent rain, making it a month of transition. With maximum highs reaching 22°C (72°F), average daily temperatures settle around a comfortable 13°C (56°F), while nights can dip to a cool 3°C (38°F). The weather is marked by high humidity at 86%, contributing to the lush greenery of the surroundings. Rainfall totals 73 mm (2.9 in), spread across approximately 14 days, adding to the charm of this coastal town. Whether you're exploring the scenic harbor or enjoying local culture, September offers a refreshing experience amid shifting weather patterns.

September Temperature in Dun Laoghaire

As September settles in Dun Laoghaire, Ireland, the air begins to transition from the summery warmth of August to the crisp embrace of autumn. With minimum temperatures averaging around 3°C (38°F), the chill is noticeable, yet the daytime remains inviting with an average high of 22°C (72°F), perfect for outdoor strolls along the picturesque coastline. This month marks a delightful equilibrium where the lingering warmth of summer still hovers, leading to an average temperature of 13°C (56°F). As the days shorten and the leaves start to turn, September invites both locals and visitors to relish in its temperate charm before the cooler months arrive.

September Weather in Dun Laoghaire: Daily Temperature Highs, Lows, and Averages

The chart illustrates September temperature patterns in Dun Laoghaire, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends.
JanFebMarAprMayJunJulAugSepOctNovDec424344475257605956514643
Data source: Temperature data for Dun Laoghaire 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 Dun Laoghaire

In Dun Laoghaire, Ireland, September typically showcases a balanced transition from summer to autumn, with a precipitation amount of 73 mm (2.9 in) falling over 14 days. This figure reflects a slight decrease from the wetter months of July and August, which average 80 mm and 95 mm respectively. Interestingly, as summer fades, September maintains a comparative moisture level similar to May and June, suggesting the persistence of Atlantic weather patterns. Following this month, rainfall tends to increase again in October and November, signaling the onset of the wetter autumn season. Overall, September holds onto the last vestiges of summer while hinting at the inviting, cooler, and rainier days ahead.

September Precipitation Trends in Dun Laoghaire

The chart displays monthly precipitation patterns in Dun Laoghaire, 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.
JanFebMarAprMayJunJulAugSepOctNovDec578081527275809573879794
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Dun Laoghaire

In Dun Laoghaire, Ireland, September brings a peak in humidity levels at 86%, aligning with the generally consistent moisture that characterizes the summer months. This slight uptick is mirrored in both July and August, where humidity also hovers at 86% and 85% respectively. As the year transitions into autumn, the trend continues with October experiencing a minor increase to 87% before settling into the slightly drier months of late autumn and winter. Overall, the data reflects a pattern of stable humidity throughout the year, with September marking the tail end of summer's lush, humid embrace.

September Average Humidity in Dun Laoghaire

This chart illustrates the average monthly humidity levels in Dun Laoghaire, 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.
JanFebMarAprMayJunJulAugSepOctNovDec85%86%86%85%83%85%86%85%86%87%87%84%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Dun Laoghaire

As September rolls into Dun Laoghaire, the UV Index settles at a moderate level of 5, indicating a need for awareness but not a severe risk for sunburn. This month marks a slight decline from the highs of summer, where July and June experienced very high UV ratings of 8. With a burn time extending to 30 minutes, residents and visitors can enjoy the lingering warmth of early autumn while still taking necessary precautions. Compared to the preceding months, September offers a comfortable transition as the days shorten, making it a perfect opportunity to enjoy outdoor activities. For a detailed understanding of the UV Index throughout the year, visit Dun Laoghaire UV Index.

Maximum UV Index Levels in Dun Laoghaire for September

The chart shows the monthly maximum UV Index (UVI) for Dun Laoghaire 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.
JanFebMarAprMayJunJulAugSepOctNovDec124578875321
Data source: Dun Laoghaire 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 Dun Laoghaire

As summer gently fades, September in Dun Laoghaire offers a delightful balance of warmth and light, with 294 hours of sunshine illuminating the coastal charm. This month marks a gradual decrease from the vibrant summer months of June and July, each boasting 385 hours, while still surpassing the relatively dimmer winter months ahead. With the sun working its magic, the crisp September air invites locals and visitors alike to bask in the beauty of the season, as shades of autumn begin to paint the landscape. The notable sunshine not only enhances the allure of this coastal town but also serves as a perfect backdrop for leisurely strolls along the waterfront, making it a cherished time before the 120 hours of November settle in.

Monthly Sunshine Duration in Dun Laoghaire: September Highlighted

The September sunshine duration represents the total number of hours Dun Laoghaire 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.
JanFebMarAprMayJunJulAugSepOctNovDec83h147h191h311h391h385h385h339h294h230h120h95h
Data source: Dun Laoghaire September Sunshine duration data generated using information from the Copernicus Climate Change Service.

Chance of Sun in Dun Laoghaire During September

In Dun Laoghaire, September presents a challenging prospect for sunshine enthusiasts, with a 20% chance of sunny weather. This slight dip not only follows the vibrant month of August, which holds a comparatively higher 23% chance, but also harks back to the somewhat shy patterns of summer and early autumn. April boasts the most promising outlook with a 44% chance of sunshine, while the chances after September, such as October with 19%, suggest a gradual decrease as the year wanes. Overall, September mirrors a transitional phase in Ireland, where the sun begins to yield to the encroaching autumn, leaving locals and visitors yearning for those fleeting rays of daylight.

Percentage of Sunny Days in September in Dun Laoghaire

The chart illustrates the percentage of sunny days in Dun Laoghaire 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 Dun Laoghaire experiences clear skies throughout the year.
JanFebMarAprMayJunJulAugSepOctNovDec23%21%22%44%31%24%30%23%20%19%26%23%
Data source: Dun Laoghaire September chance of sun data, generated using information from the Copernicus Climate Change Service.

Daylight Hours in Dun Laoghaire in September

As September arrives in Dun Laoghaire, Ireland, daylight begins to gradually wane, transitioning from the long, sun-drenched days of summer. With an average of 12 hours of daylight, the month presents a gentle shift, allowing residents and visitors alike to savor the lingering warmth of early autumn. This dip from the 16 hours of daylight in July and August highlights the impending changes of the seasons, where the lush vibrancy gives way to the crisp air of fall. Following September, daylight is expected to further decrease, settling to 10 hours in October and dropping to 8 hours by November. This rhythmic ebb and flow of daylight captures the essence of life in Dun Laoghaire, reminding us of nature's delicate balance through the year.

Average Daylight Hours in Dun Laoghaire for September

The chart illustrates the variation in daylight duration in Dun Laoghaire throughout the year, with September highlighted. It shows the monthly changes in daylight hours, calculated by summing the hours between sunrise and sunset.
JanFebMarAprMayJunJulAugSepOctNovDec8h 7m9h 49m11h 54m14h 2m15h 54m16h 53m16h 22m14h 40m12h 37m10h 30m8h 36m7h 34m
Data source: Dun Laoghaire daylight hours, calculated by summing the hours between sunrise and sunset for each day.

September Winds in Dun Laoghaire

As summer gently transitions to autumn, September in Dun Laoghaire experiences a notable shift in wind patterns. With an average wind speed of 3.4 m/s (8 mph), September maintains a soft breeze reminiscent of the previous month, August, yet signals the onset of slightly brisker days ahead. This period of moderate wind follows a summer of calm, characterized by July's lowest average of 2.7 m/s (6 mph). Interestingly, as the year continues, wind speeds are set to gradually increase, peaking in October and November at around 4.9 m/s (11 mph). This trend sets a dynamic backdrop for the coastal charm of Dun Laoghaire, inviting both locals and visitors to relish the invigorating air as the seasons change.

Average September Wind Speed in Dun Laoghaire

The chart displays monthly wind speed patterns in Dun Laoghaire, 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.
JanFebMarAprMayJunJulAugSepOctNovDec4.56.04.73.44.03.72.73.63.4 m/s4.94.84.9
Data source: Dun Laoghaire September wind data, generated using information from the Copernicus Climate Change Service.

How September Weather in Dun Laoghaire Compares to Other Months

The weather in Dun Laoghaire 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 Dun Laoghaire and find detailed weather information for every month.

In September, the weather in Dun Laoghaire is generally milder, with temperatures ranging from a minimum of 3°C (38°F) to a maximum of 22°C (72°F) and an average of 13°C (56°F). This month sees about 73 mm (2.9 in) of precipitation spread over 14 days, contributing to a relatively high humidity level of 86%. In contrast, January brings colder conditions, with temperatures dropping to a low of -3°C (26°F) and peaking at 13°C (56°F), giving an average of 5°C (42°F). Precipitation is slightly lower at 57 mm (2.2 in), occurring over 10 days, and humidity remains similar at 85%. For a closer look at the specifics of January weather, you can visit Dun Laoghaire weather in January.

The weather in September is generally milder compared to February, with average temperatures ranging from a minimum of 3°C (38°F) to a maximum of 22°C (72°F), while February experiences cooler conditions, with a minimum of -2°C (29°F) and a maximum of 14°C (58°F). Both months see a similar amount of precipitation, approximately 73 mm (2.9 in) in September and 80 mm (3.1 in) in February, with rainfall occurring on about 14 days in each month. Interestingly, humidity levels remain constant at 86% for both September and February, contributing to a consistently damp feel. For more detailed insights on winter conditions, visit Dun Laoghaire weather in February.

September and March exhibit notable differences in weather patterns, despite both months experiencing similar humidity levels of 86%. In September, temperatures range from a mild minimum of 3°C (38°F) to a comfortable maximum of 22°C (72°F), while March presents a cooler profile with minimum temperatures dropping as low as -5°C (24°F) and maximums reaching only 16°C (61°F). Precipitation is slightly higher in March, with a total of 81 mm (3.2 in) over 15 rainy days compared to September's 73 mm (2.9 in) over 14 days. This makes March a wetter month, while September tends to offer warmer and more pleasant weather. For more detailed insights, you can refer to Dun Laoghaire weather in March.

September and April present distinct weather patterns. In September, temperatures range from a minimum of 3°C (38°F) to a maximum of 22°C (72°F), with an average of 13°C (56°F), while April is cooler, with temperatures dipping as low as -2°C (29°F) and peaking at 19°C (66°F), averaging 8°C (47°F). Precipitation is more abundant in September, with 73 mm (2.9 in) occurring over 14 days compared to April's 52 mm (2.0 in) across 11 days. Both months show high humidity levels, with September at 86% and April slightly lower at 85%. For more detailed information, you can check Dun Laoghaire weather in April.

When comparing the weather in September and May, both months exhibit mild temperatures but showcase different characteristics. September enjoys a slightly higher average temperature of 13°C (56°F) compared to May's average of 11°C (52°F), with September's maximum temperature reaching 22°C (72°F) just above May's peak of 21°C (71°F). Interestingly, both months experience similar precipitation levels, around 72-73 mm (2.8-2.9 in), and both have roughly 14 days of rainfall. However, September's humidity is slightly higher at 86% compared to May's 83%, contributing to a more humid feel in early autumn. For those interested in the weather specifics of May, further details can be found here: Dun Laoghaire weather in May.

In comparing the weather of September and June, we see some notable differences. September tends to be cooler, with average temperatures ranging from a minimum of 3°C (38°F) to a maximum of 22°C (72°F), while June offers slightly warmer conditions, with a minimum of 6°C (42°F) and a maximum of 24°C (75°F). Precipitation levels are similar in both months, with September receiving 73 mm (2.9 in) over 14 days and June experiencing 75 mm (3.0 in) over 15 days. Humidity is also quite comparable, hovering around 86% in September and 85% in June. For those interested in a deeper look at June's climate specifics, you can explore Dun Laoghaire weather in June.

In comparing the weather between July and September, July tends to be warmer overall, with average temperatures ranging from a minimum of 8°C (46°F) to a maximum of 25°C (77°F). In contrast, September experiences cooler conditions, with temperatures ranging from a minimum of 3°C (38°F) to a maximum of 22°C (72°F). Both months see similar levels of precipitation, with July receiving 80 mm (3.2 in) and September receiving slightly less at 73 mm (2.9 in), though both months experience rain on about 14 days. Notably, the humidity remains constant at 86% for both months, contributing to a damp atmosphere as summer gives way to autumn. For more detailed insights, check out Dun Laoghaire weather in July.

In comparison to August, September experiences cooler temperatures with a minimum of 3°C (38°F) and an average of 13°C (56°F), making it distinctly chillier than August, which has a minimum of 7°C (45°F) and an average of 15°C (60°F). While the maximum temperature in both months is relatively similar, with September peaking at 22°C (72°F) and August at 23°C (73°F), September sees slightly less precipitation overall, totaling 73 mm (2.9 in) over 14 days compared to August's 95 mm (3.8 in) across 16 days. Humidity levels remain close, with September at 86% and August at 85%, contributing to a consistently damp atmosphere. For more specific details on August's climate, check out Dun Laoghaire weather in August.

September and October present a noticeable shift in weather conditions, with October generally being cooler and slightly wetter. In September, temperatures range from a minimum of 3°C (38°F) to a maximum of 22°C (72°F), with an average of 13°C (56°F), while October sees a decrease in temperatures to a minimum of 1°C (35°F) and a maximum of 18°C (65°F), averaging 11°C (51°F). Both months experience similar levels of precipitation, with September receiving 73 mm (2.9 in) and October slightly higher at 87 mm (3.4 in), yet both have rainfall spread over about 14 days. The humidity remains consistent, with September at 86% and October at 87%. For more detailed information, you can view the Dun Laoghaire weather in October.

September and November weather exhibit noticeable differences in temperature and precipitation. In September, temperatures range from a minimum of 3°C (38°F) to a maximum of 22°C (72°F), with an average of 13°C (56°F). The month receives about 73 mm (2.9 in) of rainfall over 14 days, while humidity remains high at 86%. In contrast, November brings cooler temperatures, with a minimum of 0°C (32°F) and a maximum of 15°C (59°F), averaging just 8°C (46°F). This month sees an increase in precipitation, totaling 97 mm (3.8 in) over the same number of rainy days. Despite the chill, humidity levels stay constant at 86%. For a more detailed look at November conditions, you can check Dun Laoghaire weather in November.

In September, the weather features a more moderate temperature range, with minimums of 3°C (38°F) and maximums reaching 22°C (72°F), averaging around 13°C (56°F). The month experiences significant humidity at 86% and sees approximately 73 mm (2.9 in) of precipitation over 14 days. In contrast, December brings cooler temperatures, with minimums dropping to -2°C (28°F) and maximums peaking at 13°C (56°F), resulting in an average of 6°C (44°F). December also has slightly higher precipitation, totaling 94 mm (3.7 in) across 15 days, with humidity levels remaining fairly consistent at 84%. For more detailed insights, check out Dun Laoghaire weather in December.

Compare Dun Laoghaire's Climate with Cities Worldwide

Conclusion: What to Expect From September Weather in Dun Laoghaire

As September unfolds in Dun Laoghaire, the weather begins to shift, inviting the transition from summer’s warmth to the crispness of autumn. With average temperatures settling around 13°C (56°F), days can still reach pleasant highs of 22°C (72°F), but cooler nights remind us that fall is on the horizon. The month typically experiences 14 days of precipitation, contributing to a notable humidity level of 86% that blankets the area in a refreshing, coastal atmosphere. This shift from the dry summer months adds a unique charm to Dun Laoghaire, making it a captivating time to explore the seaside. To learn more about how September weather contrasts with the rest of the year, check out the detailed insights on Dun Laoghaire Climate.