January in Mainz averages a daily high of 4.6°C with nights around 0°C. Expect roughly 12.6 wet days totalling 43.5mm. A hard month to visit for comfort alone.
Across the year, the best time to visit Mainz is May–September.
Based on MAINZ LERCHENBERG ZDF, GM (5.1km), 1995–2024. 29 years of January data.