September Weather in Belfast, United States

Last updated: June 24, 2025

In September, the average temperature in Belfast, United States is a comfortable 16°C (61°F), with a minimum dipping to 3°C (38°F) and a maximum reaching 29°C (84°F). Expect about 77 mm (3.0 in) of precipitation spread over 8 days, contributing to a relatively high average humidity of 77%.

September Temperature in Belfast

In September in Belfast, the average temperature is 16°C (61°F). The maximum can reach 29°C (84°F), and the minimum can be as low as 3°C (38°F). This makes Belfast a comfortable destination for travelers looking to enjoy moderate weather.

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

The chart illustrates September temperature patterns in Belfast, showcasing daily minimum, maximum, and average temperatures. It highlights the typical range of temperatures throughout the month, providing insights into weather trends. In Belfast, September typically has an average temperature of 16°C (61°F), with highs reaching up to 29°C (84°F) and lows dropping to around 3°C (38°F).

Data source: Temperature data for Belfast generated using information from the Copernicus Climate Change Service.

September Precipitation in Belfast

In Belfast in September, the precipitation amount is 77 mm (3.0 in) distributed over 8 days.

September Precipitation Trends in Belfast

The chart displays monthly precipitation patterns in Belfast, 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 Belfast, September typically receives around 77 mm (3.0 inches) of precipitation spread over approximately 8 days.

Data source: Precipitation data for September generated using information from the Copernicus Climate Change Service.

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Millimeters (mm) Inches (in)

September Humidity in Belfast

In Belfast in September humidity is 77%. With an average temperature of 16°C (61°F), this humidity feels like a slight heaviness in the air, making every step feel a touch more effortful while traveling. The dampness clings to your skin, adding a layer of discomfort, yet the mild temperature invites you to explore the surroundings, blending the challenge of the humidity with an opportunity for a refreshing adventure.

September Average Humidity in Belfast

This chart illustrates the average monthly humidity levels in Belfast, 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 Belfast is approximately 77%, offering insight into how humid the weather typically is during this month.

Data source: Humidity data for September generated using information from the Copernicus Climate Change Service.

September UV Index in Belfast

In Belfast in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, you can check the Hourly UV Index in Belfast.

Maximum UV Index Levels in Belfast for September

The chart shows the monthly maximum UV Index (UVI) for Belfast 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 Belfast typically reaches 7, which falls under the high exposure category.

Data source: Belfast 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 Belfast Compares to Other Months

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

This table compares monthly weather conditions in Belfast, showing how September’s temperature, precipitation, humidity, and UV index levels differ from those of other months.
	Temperature	Precipitation	Humidity	UV
January Weather	-4°C (24°F)	93 mm (3.7 inches)	88%	low
February Weather	-4°C (26°F)	88 mm (3.5 inches)	88%	moderate
March Weather	0°C (32°F)	72 mm (2.9 inches)	85%	moderate
April Weather	6°C (43°F)	131 mm (5.2 inches)	81%	high
May Weather	11°C (53°F)	90 mm (3.6 inches)	76%	very high
June Weather	17°C (63°F)	76 mm (3.0 inches)	74%	very high
July Weather	20°C (68°F)	91 mm (3.6 inches)	74%	very high
August Weather	20°C (68°F)	75 mm (3.0 inches)	74%	very high
September Weather	16°C (61°F)	77 mm (3.0 inches)	77%	high
October Weather	11°C (51°F)	130 mm (5.1 inches)	82%	moderate
November Weather	3°C (38°F)	121 mm (4.8 inches)	85%	moderate
December Weather	-2°C (28°F)	129 mm (5.1 inches)	84%	low