December in La Mesa averages a daily high of 20.9°C with nights around 6°C. Expect roughly 5.4 wet days totalling 51.3mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit La Mesa is March–June.
Based on EL CAJON, CA US (9.6km), 1995–2024. 25 years of December data.