December in Oceanside averages a daily high of 17.4°C with nights around 8°C. Expect roughly 4.7 wet days totalling 42.4mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Oceanside is May–November.
Based on OCEANSIDE MARINA, CA US (2.1km), 1995–2024. 24 years of December data.