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September Weather in Boston, Ireland

Last updated: August 23, 2025

In Boston, Ireland, the average temperature in September hovers around 13°C (56°F), with a comfortable range between a minimum of 2°C (36°F) and a maximum of 26°C (80°F). Expect 102 mm (4.0 in) of precipitation spread across 16 days, contributing to an average humidity level of 88%. Prepare for a month that balances cool breezes with occasional rainy spells!

September Temperature in Boston

In September in Boston, the average temperature is 13°C (56°F). The maximum can reach 26°C (80°F), and the minimum can be as low as 2°C (36°F). This climate offers comfortable weather for exploring the outdoors or enjoying local attractions.

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

The chart illustrates September temperature patterns in Boston, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Boston, September typically has an average temperature of 13°C (56°F), with highs reaching up to 26°C (80°F) and lows dropping to around 2°C (36°F).
JanFebMarAprMayJunJulAugSepOctNovDec434445485357605956514745
Data source: Temperature data for Boston 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 Boston

In Boston in September, the precipitation amount is 102 mm (4.0 in) spread over 16 days.

September Precipitation Trends in Boston

The chart displays monthly precipitation patterns in Boston, 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 Boston, September typically receives around 102 mm (4.0 inches) of precipitation spread over approximately 16 days.
JanFebMarAprMayJunJulAugSepOctNovDec8613811261687684133102121105131
Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.
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September Humidity in Boston

In Boston in September, humidity is 88%. With an average temperature of 13°C (56°F), this humidity feels like a thick, warm blanket wrapping around you, making outdoor adventures sticky and challenging.

September Average Humidity in Boston

This chart illustrates the average monthly humidity levels in Boston, 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 Boston is approximately 88%, offering insight into how humid the weather typically is during this month.
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 Boston

In Boston in September, the maximum UV index reaches 5, which corresponds to a moderate Exposure Category. Under these conditions, the estimated time to burn is approximately 30 minutes. For more details, you can check the Hourly UV Index in Boston.

Maximum UV Index Levels in Boston for September

The chart shows the monthly maximum UV Index (UVI) for Boston 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 Boston typically reaches 5, which falls under the moderate exposure category.
JanFebMarAprMayJunJulAugSepOctNovDec124578875321
Data source: Boston 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.

How September Weather in Boston Compares to Other Months

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

This table compares monthly weather conditions in Boston, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
 TemperaturePrecipitationHumidityUV
January Weather6°C (44°F)86 mm (3.4 inches)88%low
February Weather7°C (44°F)138 mm (5.4 inches)88%low
March Weather7°C (45°F)112 mm (4.4 inches)87%moderate
April Weather9°C (49°F)61 mm (2.4 inches)86%moderate
May Weather12°C (53°F)68 mm (2.7 inches)83%high
June Weather14°C (57°F)76 mm (3.0 inches)83%very high
July Weather16°C (60°F)84 mm (3.3 inches)85%very high
August Weather15°C (59°F)133 mm (5.2 inches)85%high
September Weather13°C (56°F)102 mm (4.0 inches)88%moderate
October Weather11°C (52°F)121 mm (4.8 inches)91%moderate
November Weather8°C (47°F)105 mm (4.1 inches)92%low
December Weather7°C (45°F)131 mm (5.2 inches)89%low

Compare Boston's Climate with Cities Worldwide