January in Leiden averages a daily high of 6.5°C with nights around 1.4°C. Expect roughly 16.5 wet days totalling 74.9mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Leiden is May–September.
Based on ROTTERDAM, NL (22.2km), 1995–2024. 30 years of January data.