December in Longueuil averages a daily high of -0.5°C with nights around -6.8°C. Expect roughly 15.9 wet days totalling 109.9mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Longueuil is May–September.
Based on MCTAVISH, QC CA (9.1km), 1995–2024. 27 years of December data.