January in Castlereagh averages a daily high of 8.1°C with nights around 2.5°C. Expect roughly 18.4 wet days totalling 87.8mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Castlereagh is June–September.
Based on STORMONT CASTLE, UK (4.9km), 1995–2024. 27 years of January data.