Belfast
United Kingdom
Long-term weather forecast
Long-term weather forecast

September weather forecast and climate
Belfast, United Kingdom

A close-up view of the Northern Ireland City Hall located in Belfast, United Kingdom
A close-up view of the Northern Ireland City Hall located in Belfast, United Kingdom
The first month of the autumn, September, is also an enjoyable month in Belfast, United Kingdom, with average temperature ranging between min 9.5°C (49.1°F) and max 16.4°C (61.5°F).

Temperature

In September, the average high-temperature is almost the same as in August - a still enjoyable 16.4°C (61.5°F). In Belfast, the average low-temperature is 9.5°C (49.1°F).

Rainfall

In Belfast, in September, during 12.6 rainfall days, 75.6mm (3") of precipitation is typically accumulated. Throughout the year, there are 157.5 rainfall days, and 860.2mm (33.9") of precipitation is accumulated.

Sea temperature

September is the month with the warmest seawater in Belfast, with an average sea temperature of 14.3°C (57.7°F).
Note: At temperatures below 10°C (50°F), swimming in a suitably protected swimsuit is feasible; otherwise, cold shock and loss of breathing control are imminent. Even a short swim, without thermal protection, at temperatures around 13°C (55.4°F) is not comfortable.

Daylight

In Belfast, the average length of the day in September is 12.7h.

Sunshine

In Belfast, the average sunshine in September is 4h.

UV index

The average daily maximum UV index in September is 3. A UV Index value of 3 to 5 symbolizes a medium health hazard from unprotected exposure to the Sun's UV rays for the ordinary person.
Note: In September, the average maximum UV index of 3 translate into the following recommendations:
Take precautions - Protection against the skin and eye damage is obliged. The Sun's most intense and consequently most harmful UV radiation during midday hours should be decreased by minimizing exposure and seeking shade. A wide-brim hat offers excellent sun protection for eyes, ears, face, and neck. Sunglasses with UVA and UVB protection significantly reduce eye damage from sun exposure. Tightly woven, loose-fitting clothes provide additional protection from the Sun.

What is the temperature in September in Belfast?

In September, in Belfast, United Kingdom, the average high-temperature is 16.4°C (61.5°F), and the average low-temperature is 9.5°C (49.1°F).

How much does it rain in Belfast in September?

In Belfast, United Kingdom, in September, it is raining for 12.6 days, with typically 75.6mm (3") of accumulated precipitation.

What month is the sea warmest in Belfast?

September is the month with the warmest seawater, with an average sea temperature of 14.3°C (57.7°F).

How cold is the water in September in Belfast?

In Belfast, in September, the average water temperature is 14.3°C (57.7°F). Swimming in 14.3°C (57.7°F) is considered dangerous. Unprotected immersion in temperatures below 10°C (50°F) causes quickly maximum intensity cold shock with hyperventilation.

What is the average length of the day in September in Belfast?

The average length of the day in September in Belfast is 12.7h.

How long on average sun shines in September in Belfast?

In September, the average sunshine in Belfast, United Kingdom, is 4h.

What is the UV index reading in September in Belfast?

The average daily maximum UV index in September in Belfast is 3. A UV Index value of 3 to 5 symbolizes a medium health risk from the exposure to the Sun's UV radiation.
Average temperature in September - Belfast, United Kingdom
  • Average high temperature in September: 16.4°C

The warmest month (with the highest average high temperature) is July (18.8°C).
The month with the lowest average high temperature is January (7.1°C).

  • Average low temperature in September: 9.5°C

The month with the highest average low temperature is July (11.7°C).
The coldest month (with the lowest average low temperature) is February (1.6°C).

Average rainfall in September - Belfast, United Kingdom
  • Average rainfall in September: 75.6mm

The wettest month (with the highest rainfall) is October (89.6mm).
The driest month (with the lowest rainfall) is May (57.3mm).

Average rainfall days in September - Belfast, United Kingdom
  • Average rainfall days in September: 12.6 days

The month with the highest number of rainy days is January (14.8 days).
The month with the lowest number of rainy days is June (11.3 days).

Average sea temperature in September - Belfast, United Kingdom
  • Average sea temperature in September: 14.3°C

The best month for swimming (with the highest average sea temperature) is September (14.3°C).
The coldest month (with the lowest average sea temperature) is March (8°C).

Average daylight in September / Average sunshine in September - Belfast, United Kingdom
  • Average daylight in September: 12.7h

The month with the longest days is June (Average daylight: 17.2h).
The month with shortest days is December (Average daylight: 7.4h).

  • Average sunshine in September: 4h

The month with most sunshine is May (Average sunshine: 6.4h).
The month with least sunshine is December (Average sunshine: 1.5h).

Average UV index in September - Belfast, United Kingdom
  • Average UV index in September: 3

Months with the highest UV index are June and July (UV index 6).
Months with the lowest UV index are January and December (UV index 0).