December in Portsmouth averages a daily high of 12.2°C with nights around 2.6°C. Expect roughly 9.8 wet days totalling 98.1mm. Generally workable, with some weather to plan around.
Across the year, the best time to visit Portsmouth is April–May.
Based on NORFOLK SOUTH, VA US (7.3km), 1995–2024. 22 years of December data.