Northern Ireland weather in September 2025

Expect daytime maximum temperatures of 16°C in Northern Ireland, UK in September based on long-term weather averages. There are 4 hours of sunshine per day on average with 17 days with some rainfall and typically 94 mm of rainfall in the month.

  • 16°C maximum daytime temperature in September in Northern Ireland (Belfast)16
    16°C max day temperature
  • 4 hours of sunshine per day
  • 17 days with some rainfall in September in Northern Ireland (Belfast)17
    17 days with some rainfall
  • 9°C minimum night-time temperature in September in Northern Ireland (Belfast)9
    9°C min night temperature
  • 13 hours of daylight per day in September in Northern Ireland (Belfast)13
    13 hours of daylight per day
  • No heat & humidity in September in Northern Ireland (Belfast)0
    No heat & humidity
  • 94 mm monthly rainfall in September in Northern Ireland (Belfast)94
    94 mm of monthly rainfall
  • UV (maximum) index 3 (Moderate) in September in Northern Ireland (Belfast)3
    3 (Moderate) UV index
  • 14°C sea temperature in September in Northern Ireland (Belfast)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.

All Northern Ireland destinations

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

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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.

JanFebMarAprMayJunJulAugSepOctNovDec

Date Sunrise times Sunset times
Monday, 1st September 2025 05:31 19:15
Monday, 15th September 2025 05:57 18:40
Tuesday, 30th September 2025 06:24 18:02

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