September in Derry averages a daily high of 16.1°C with nights around 11.3°C. Expect roughly 19.2 wet days totalling 91.7mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Derry is June–September.
Based on MALIN HEAD, EI (41.6km), 1995–2024. 30 years of September data.