April in Mainz averages a daily high of 16.3°C with nights around 6.3°C. Expect roughly 9.9 wet days totalling 37.8mm. Generally workable, with some weather to plan around.
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 April data.