September in Lowell averages a daily high of 24.4°C with nights around 11.2°C. Expect roughly 8.9 wet days totalling 99.5mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Lowell is May–June.
Based on LOWELL, MA US (4km), 1995–2024. 28 years of September data.