September Weather in Castlebar, Ireland

Last updated: March 17, 2025

In September, Castlebar, Ireland experiences a diverse range of weather conditions. With a maximum temperature reaching 25°C (77°F) and an average of 13°C (56°F), the month provides a pleasant mix of warmth and coolness. However, cooler nights can be expected, with minimum temperatures dropping to 2°C (35°F). Rain is a common feature, with a total precipitation of 92 mm (3.6 in) spread over 17 days, contributing to a high humidity level of 88%. This combination creates a uniquely dynamic climate, ideal for both outdoor activities and indoor relaxation amidst the scenic Irish landscape.

September Temperature in Castlebar

In Castlebar, Ireland, September marks a delightful transition into autumn, offering a refreshing blend of warmth and crispness. The temperatures during this month range from a comfortable minimum of 2°C (35°F) to a pleasant maximum of 25°C (77°F), with an average hovering around 13°C (56°F). This gradual decline from the summer heat is exemplified as temperatures dip from August’s highs, making way for cooler, more invigorating breezes. As the month progresses, you can expect shorter days and the landscape transitioning into a vibrant tapestry of autumnal colors, perfect for outdoor exploration against a backdrop of increasingly fresh air. Overall, September in Castlebar provides a balanced climate, inviting locals and visitors alike to enjoy the beauty of the season.

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

The chart illustrates September temperature patterns in Castlebar, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends.
JanFebMarAprMayJunJulAugSepOctNovDec434344485256595855504644
Data source: Temperature data for Castlebar generated using information from the Copernicus Climate Change Service.
Choose your preferred temperature unit
The average of daily temperatures (24 hours) calculated across all days in the month.

September Precipitation in Castlebar

September in Castlebar, Ireland, typically ushers in a noticeable transition in its weather patterns. With 92 mm (3.6 inches) of precipitation spread over 17 days, it retains a healthy share of rainfall, reminiscent of the wet August that preceded it. This month’s rainfall, while slightly lighter than August's hefty 133 mm (5.3 inches), still contributes to a lush, green landscape as the days begin to shorten. The consistent precipitation hints at the onset of autumn, paving the way for the wetter months ahead, such as October, which often sees rainfall reach 127 mm (5.0 inches). Overall, while September showcases a balance between summer's lingering moisture and the emerging chill of fall, it serves as a reminder of the distinctive, ever-changing character of Castlebar's climate.

September Precipitation Trends in Castlebar

The chart displays monthly precipitation patterns in Castlebar, 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.
JanFebMarAprMayJunJulAugSepOctNovDec871351076374879113392127110121
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Castlebar

September in Castlebar, Ireland, signals a return to higher humidity levels, reaching 88%, a figure consistent with the earlier months of the year. Following a trend seen from January through August, where humidity fluctuated between 83% and 88%, September marks a notable increase as the summer warmth fades. The month serves as a bridge as the air begins to gather moisture ahead of the cooler autumn days, setting the stage for an even higher average humidity of 91% in October. This trend underscores Castlebar's characteristic dampness, particularly as the year transitions towards the wetter months ahead.

September Average Humidity in Castlebar

This chart illustrates the average monthly humidity levels in Castlebar, 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%87%86%83%83%85%85%88%91%92%89%
Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Castlebar

As summer's warmth gently wanes into autumn, September in Castlebar, Ireland, presents a moderate UV Index of 5, signifying a shift towards safer sun exposure levels. This month, the burn time extends to a more manageable 30 minutes, encouraging outdoor enthusiasts to savor the lingering rays while practicing sun safety. Following the peak levels of 8 in June and July, September’s index reflects a gradual decline that sets the tone for the cooler months ahead. Those enjoying the gentle sun should remain mindful of UV exposure, especially as daylight decreases. For more detailed information and to plan your sun-safe activities, check the Castlebar UV Index.

Maximum UV Index Levels in Castlebar for September

The chart shows the monthly maximum UV Index (UVI) for Castlebar 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: Castlebar 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 Castlebar

As summer gently wanes, September in Castlebar, Ireland, holds a special charm with 284 hours of sunshine, a delightful transition from the warmer months. While the sun-soaked days of May, with a remarkable 396 hours, shift gradually into autumn, September still offers a generous amount of light compared to October's 220 hours. This month showcases nature's brilliance as the lush landscapes begin to shift hues, inviting residents and visitors alike to bask in the temperate days before the colder months set in. The decline in sunlight hours after September hints at the coming winter, making this time feel particularly precious as the community gathers to enjoy the last vestiges of summer's warmth.

Monthly Sunshine Duration in Castlebar: September Highlighted

The September sunshine duration represents the total number of hours Castlebar 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.
JanFebMarAprMayJunJulAugSepOctNovDec72h136h185h316h396h380h382h334h284h220h114h91h
Data source: Castlebar September Sunshine duration data generated using information from the Copernicus Climate Change Service.

Chance of Sun in Castlebar During September

In Castlebar, Ireland, September brings a moderate likelihood of sunny weather, with only a 14% chance of sunshine. This trend reflects a gradual decline from the early spring and summer months, where the chances peak at 40% in April before dropping through the warmer months. While September marks the transition into autumn, the sunshine levels closely resemble those of March and even January, suggesting that any outdoor plans may be met with a mix of cloud cover and rain rather than a bright, sunny backdrop. As the year progresses, the overall chances fluctuate, but September's relatively low probability indicates that visitors should be prepared for typical Irish weather, where clear skies are far from guaranteed.

Percentage of Sunny Days in September in Castlebar

The chart illustrates the percentage of sunny days in Castlebar 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 Castlebar experiences clear skies throughout the year.
JanFebMarAprMayJunJulAugSepOctNovDec27%19%14%40%35%16%23%19%14%17%22%14%
Data source: Castlebar September chance of sun data, generated using information from the Copernicus Climate Change Service.

Daylight Hours in Castlebar in September

As September graces Castlebar, Ireland, daylight begins to wane from the summer's vibrant heights. The month offers approximately 12 hours of daylight, a gentle transition from the 16 hours enjoyed in June and July. This gradual decrease paves the way for the autumn months, reflecting a broader trend where daylight ebbs from a peak in mid-year to a modest 8 hours by November. September's daylight, while shorter than summer's bounty, still provides ample opportunity for exploring the rich landscape adorned in early autumn colors, reminding us of the cyclical rhythm of nature as we prepare for the cozy embrace of fall.

Average Daylight Hours in Castlebar for September

The chart illustrates the variation in daylight duration in Castlebar throughout the year, with September highlighted. It shows the monthly changes in daylight hours, calculated by summing the hours between sunrise and sunset.
JanFebMarAprMayJunJulAugSepOctNovDec8h 5m9h 48m11h 54m14h 3m15h 57m16h 57m16h 24m14h 42m12h 37m10h 29m8h 34m7h 31m
Data source: Castlebar daylight hours, calculated by summing the hours between sunrise and sunset for each day.

September Winds in Castlebar

In September, Castlebar experiences a gentle breeze with an average wind speed of 3.3 m/s (7 mph), marking a subtle lull as summer transitions to autumn. This slight decrease in wind speed aligns with the pattern seen over the warmer months, where July recorded the lowest average wind at 2.6 m/s (6 mph). As the year progresses into the later months, wind speeds begin to rise again, peaking at 4.7 m/s (10 mph) in December. This gradual increase following September indicates a shift in atmospheric conditions as the colder months approach, creating a dynamic interplay that adds depth to Castlebar's weather. Overall, September serves as a serene pause before the invigorating winds of fall begin to sweep through the region.

Average September Wind Speed in Castlebar

The chart displays monthly wind speed patterns in Castlebar, 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.
JanFebMarAprMayJunJulAugSepOctNovDec3.65.54.63.53.83.72.63.43.3 m/s4.24.34.7
Data source: Castlebar September wind data, generated using information from the Copernicus Climate Change Service.

How September Weather in Castlebar Compares to Other Months

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

In September, the weather is generally milder, with temperatures ranging from a minimum of 2°C (35°F) to a maximum of 25°C (77°F), while January experiences colder conditions, with temperatures dipping as low as -3°C (27°F) and peaking at only 14°C (57°F). Both months see similar levels of humidity at 88%, but September has a higher average temperature of 13°C (56°F) compared to January's average of 6°C (43°F). Precipitation is fairly consistent between the two months, with September receiving 92 mm (3.6 in) over 17 days and January slightly less at 87 mm (3.4 in) over 13 days. For more detailed information, you can visit Castlebar weather in January.

September and February present contrasting weather patterns. In September, temperatures range from a mild 2°C (35°F) at night to a pleasant high of 25°C (77°F) during the day, averaging around 13°C (56°F). The month experiences 92 mm (3.6 in) of precipitation over approximately 17 days, while maintaining high humidity at 88%. In contrast, February is colder, with minimum temperatures dipping to -3°C (26°F), an average of 6°C (43°F), and highs reaching only 15°C (59°F). This month sees increased rainfall, totaling 135 mm (5.3 in) over about 18 days, while humidity remains consistent at 88%. For a closer look at February's weather specifics, check Castlebar weather in February.

September and March present contrasting weather patterns. September features a milder climate with temperatures ranging from a minimum of 2°C (35°F) to a maximum of 25°C (77°F), averaging around 13°C (56°F). This month experiences 92 mm (3.6 in) of precipitation over 17 days and a high humidity level of 88%. In contrast, March is chillier, with temperatures dipping as low as -5°C (24°F) and peaking at 17°C (62°F), with an average of 7°C (44°F). Although March sees a slightly higher rainfall totaling 107 mm (4.2 in) over 16 days, the humidity remains comparable at 87%. For a detailed look at the weather in March, you can explore Castlebar weather in March.

In September, the weather tends to be warmer, with average temperatures ranging from a minimum of 2°C (35°F) to a maximum of 25°C (77°F), while April experiences cooler conditions with temperatures ranging from -2°C (28°F) to 20°C (69°F). September also has a higher average humidity level at 88%, compared to April's 86%. Furthermore, September sees more rainfall, with 92 mm (3.6 in) of precipitation over 17 days, whereas April has 63 mm (2.5 in) across 11 days. For more detailed weather insights specifically for April, visit Castlebar weather in April.

When comparing the weather in September and May, we see some notable differences. September generally features a broader temperature range, with minimums around 2°C (35°F) and maximums reaching up to 25°C (77°F), while May has slightly colder minimums at -2°C (29°F). Both months experience similar maximum temperatures of 25°C (77°F). Precipitation is also more prolific in September, with 92 mm (3.6 in) over 17 days, compared to May's 74 mm (2.9 in) over 14 days. Additionally, September tends to be more humid, with levels around 88%, as opposed to May's 83%. For more specific information about May weather in Castlebar, you can refer to Castlebar weather in May.

When comparing the weather in September to June, several key differences emerge. September tends to be slightly cooler, with minimum temperatures averaging around 2°C (35°F) compared to June's minimum of 5°C (41°F). June generally sees a higher maximum temperature, averaging 28°C (84°F) versus September’s 25°C (77°F). Precipitation levels are relatively similar, with September receiving 92 mm (3.6 in) and June 87 mm (3.4 in), both experiencing precipitation on about 17 days. Interestingly, humidity levels in September are higher at 88%, while June has a slightly lower humidity of 83%. For more detailed information about June weather, you can check out Castlebar weather in June.

When comparing the weather between September and July, we see notable differences in temperature and overall conditions. September experiences a wider range of temperatures, with a minimum of 2°C (35°F) and a maximum of 25°C (77°F), resulting in a comfortable average temperature of 13°C (56°F). In contrast, July has milder minimum temperatures starting at 7°C (44°F) and can reach up to 28°C (83°F), with a slightly higher average of 15°C (59°F). Both months receive similar amounts of precipitation, with September getting about 92 mm (3.6 in) over 17 days and July at 91 mm (3.6 in) over 15 days. Humidity levels are slightly higher in September at 88%, compared to July's 85%. For more details on July weather, you can check Castlebar weather in July.

In comparing the weather of September and August, September tends to be cooler overall, with average temperatures ranging from a minimum of 2°C (35°F) to a maximum of 25°C (77°F), while August experiences slightly warmer conditions with temperatures from a minimum of 6°C (43°F) to a maximum of 23°C (74°F). Precipitation levels in September are lower, totaling 92 mm (3.6 in) over 17 days, compared to August's 133 mm (5.3 in) over 21 days, suggesting that September may offer a drier experience for outdoor activities. Interestingly, September also features a higher humidity level at 88%, compared to August's 85%, which can make the cooler air feel more damp. For a more detailed look at August weather specifics, visit Castlebar weather in August.

In comparing the weather between September and October, we can observe a distinct shift in temperatures and precipitation levels. September experiences a wider range of temperatures, with a minimum of 2°C (35°F), an average of 13°C (56°F), and a maximum of 25°C (77°F). The month sees about 92 mm (3.6 in) of rainfall spread over 17 days, coupled with a high humidity level of 88%.

In contrast, October brings cooler conditions, with temperatures dropping to a minimum of 0°C (33°F), an average of 10°C (51°F), and a maximum of 20°C (68°F). This month is also wetter, with precipitation increasing to 127 mm (5.0 in) over 20 days and a slight rise in humidity to 91%. For a more detailed look at the weather specifics, you can visit Castlebar weather in October.

In September, the weather is generally milder, with temperatures ranging from a low of 2°C (35°F) to a high of 25°C (77°F) and an average temperature of 13°C (56°F). The month experiences 92 mm (3.6 in) of precipitation over 17 days, accompanied by a high humidity of 88%. In contrast, November brings cooler conditions, with temperatures dipping to a minimum of -2°C (29°F) and peaking at 15°C (59°F), leading to an average of 8°C (46°F). Precipitation increases slightly to 110 mm (4.3 in) over the same number of days. The humidity also rises to 92%, making November feel significantly chillier than September. For more detailed information, you can check Castlebar weather in November.

In September, temperatures in Castlebar range from a minimum of 2°C (35°F) to a maximum of 25°C (77°F), with an average of 13°C (56°F). During this month, the area experiences around 92 mm (3.6 in) of precipitation over 17 days, accompanied by a high humidity level of 88%. Meanwhile, December brings cooler conditions, with temperatures dipping to a minimum of -3°C (27°F) and peaking at 13°C (55°F), averaging 7°C (44°F). Rainfall increases to 121 mm (4.8 in) across 19 days, while humidity remains slightly higher at 89%. The contrast between the warmer, wetter September and the colder, wetter December highlights the seasonal shift in Castlebar's weather. For more details, check out Castlebar weather in December.

Compare Castlebar's Climate with Cities Worldwide

Conclusion: What to Expect From September Weather in Castlebar

As September settles in, Castlebar experiences a distinct transition from the warmth of summer, bringing cooler temperatures that average around 13°C (56°F). While occasional peaks reaching 25°C (77°F) can provide fleeting warmth, the month is characterized by a notable increase in precipitation, with around 92 mm (3.6 in) spread over 17 days. Coupled with a high humidity of 88%, the weather feels more moist and temperate, marking a shift towards the crispness of autumn. For those interested in a deeper dive into the seasonal changes and how they shape overall climate patterns, visit Castlebar Climate.