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 61°F 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.

61
61°F max day temperature
4
4 hours of sunshine per day
17
17 days with some rainfall
48
48°F min night temperature
13
13 hours of daylight per day
0
No heat & humidity
3.7
3.7 inches of monthly rainfall
3
3 (Moderate) UV index
57
57°F sea temperature

More about Belfast

Belfast by month

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

Recommended for Belfast

Sykes Cottages: Top offers on UK cottage holidays

Sale

Browse latest special offers on UK cottage holidays
Filter deals by region, price, party size & features
Alternative search for cottages by specific travel dates

Go to Sykes Cottages deal >>

View all Sykes Cottages 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) | Imperial (°F)