Belfast weather in September 2025

Q: How warm is it in Belfast in September?

Daytime temperatures usually reach 16°C in Belfast in September, falling to 9°C at night.

Q: How sunny is it in Belfast in September?

There are normally 4 hours of bright sunshine each day in Belfast in September - that's 30% of daylight hours.

Q: How warm is the sea around Belfast in September?

The average sea temperature around Belfast in September is 14°C.

Q: Does it rain in Belfast in September?

There are usually 17 days with some rain in Belfast in September and the average monthly rainfall is 94mm.

Expect 16°C daytime maximum temperatures in the shade with on average 4 hours of sunshine per day in Belfast in September. Check more long-term weather averages for Belfast in September before you book your next holiday to Northern Ireland in 2025/2026.

16
16°C max day temperature
4
4 hours of sunshine per day
17
17 days with some rainfall
9
9°C min night temperature
13
13 hours of daylight per day
0
No heat & humidity
94
94 mm of monthly rainfall
3
3 (Moderate) UV index
14
14°C sea temperature

More about Belfast

Belfast by month

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Recommended for Belfast

National Trust Holidays: 10% off tiny cottages

Sale

Save 10% on tiny cottages with National Trust Holidays
Book breaks to North Wales, Cornwall, Suffolk & beyond
Travel between 1st Jan & 28th Feb 2025 (inclusive)

Go to National Trust Holidays deal >>

Expires at 23:59 on Friday 28th Feb 2025 · View all National Trust Holidays offers

The September weather guide for Northern Ireland (Belfast) shows long term weather averages processed from data supplied by CRU (University of East Anglia), the Met Office & the Netherlands Meteorological Institute. Find out more about our data sources.

Metric (°C / mm) | Imperial (°F / inches)