Belfast weather by month
Belfast runs from about 5°C in January to 15°C in August, with August the wettest month at 143 mm.
warmest month
August
15°C
coolest month
January
5°C
wettest month
August
143 mm
worst air month
March
6 µg/m³
The whole year, month by month.
| Month | Avg temp | Rain | Sun | PM2.5 |
|---|---|---|---|---|
| January | 5°C | 52 mm | 114 h | 4 |
| February | 7°C | 63 mm | 137 h | 5 |
| March | 7°C | 126 mm | 183 h | 6 |
| April | 8°C | 114 mm | 237 h | 5 |
| May | 13°C | 77 mm | 307 h | 4 |
| June | 13°C | 56 mm | 299 h | 4 |
| July | 14°C | 100 mm | 284 h | 4 |
| August | 15°C | 143 mm | 293 h | 5 |
| September | 12°C | 59 mm | 235 h | 4 |
| October | 11°C | 79 mm | 161 h | 6 |
| November | 8°C | 52 mm | 99 h | 3 |
| December | 7°C | 75 mm | 88 h | 5 |
About 2,437 hours of sun a year. Roughly 100 rainy days a year.
These are long-run climate normals, not a forecast. A given year can sit well outside them. PM2.5 is a global model: near the coast it counts sea salt as fine particulate and reads high against ground stations, sometimes by a factor of two. Use the shape of the year, not the absolute number.
where these numbers come from
- · Temperature, rainfall and sunshine: ECMWF ERA5 reanalysis climate normals via Open-Meteo (CC BY 4.0), fetched once and stored.
- · PM2.5: Copernicus CAMS reanalysis, monthly means. Modelled, not station readings; near coasts CAMS counts sea salt as PM2.5 and reads high.
Last reviewed 2026-05-23. Full method, licences and the list of sources we rejected are on the methodology page.