September in Brookline averages a daily high of 24.3°C with nights around 13.1°C. Expect roughly 9.2 wet days totalling 94.4mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Brookline is May–June.
Based on JAMAICA PLAIN, MA US (3.2km), 1995–2024. 27 years of September data.