December in Portland averages a daily high of 3.5°C with nights around -5.5°C. Expect roughly 12.5 wet days totalling 115.9mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Portland is June–September.
Based on PORTLAND JETPORT, ME US (4km), 1995–2024. 30 years of December data.