September in Trenton averages a daily high of 25.4°C with nights around 14.5°C. Expect roughly 8.5 wet days totalling 105.7mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Trenton is May–June.
Based on TRENTON MERCER AIRPORT, NJ US (9.1km), 1995–2024. 27 years of September data.