September in New Haven averages a daily high of 24.4°C with nights around 14.7°C. Expect roughly 9.2 wet days totalling 103.2mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit New Haven is May–June.
Based on NEW HAVEN TWEED AIRPORT, CT US (6.4km), 1995–2024. 23 years of September data.