January in Lahti averages a daily high of -3.5°C with nights around -9°C. Expect roughly 16.6 wet days totalling 46mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Lahti is June–August.
Based on HEINOLA ASEMANTAUS, FI (32km), 1995–2024. 30 years of January data.