May in Oslo averages a daily high of 16.7°C with nights around 6.8°C. Expect roughly 12.5 wet days totalling 63.8mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Oslo is June–September.
Based on OSLO BLINDERN, NO (3.6km), 1995–2024. 30 years of May data.