Northern Ireland weather in September 2025

Q: How warm is it in Northern Ireland in September?

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

Q: How sunny is it in Northern Ireland in September?

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

Q: How warm is the sea around Northern Ireland in September?

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

Q: Does it rain in Northern Ireland in September?

There are usually 17 days with some rain in Belfast, Northern Ireland 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 Northern Ireland in September. Check more long-term weather averages for Northern Ireland 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

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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.

Top Northern Ireland destinations

Below are average maximum temperatures at popular countries, regions and places in Northern Ireland in September. Select a holiday destination to see more weather parameters.

16
Belfast
15
Londonderry

All Northern Ireland destinations

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

More about the UK

How warm is it in Northern Ireland in September?

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

How sunny is it in Northern Ireland in September?

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

How warm is the sea around Northern Ireland in September?

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

Does it rain in Northern Ireland in September?

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

Northern Ireland September sunrise & sunset times

Browse the sunrise and sunset times for Northern Ireland in September 2025. Select a month to view Northern Ireland sunrise and sunset times for the next 12 months. The Northern Ireland sunrise and sunset times shown below are for Belfast.

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