May in Waltham averages a daily high of 20.8°C with nights around 7.9°C. Expect roughly 12.6 wet days totalling 81.6mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Waltham is May–June.
Based on BEDFORD HANSCOM FIELD, MA US (11.3km), 1995–2024. 26 years of May data.