September in Newmarket averages a daily high of 22.1°C with nights around 9.8°C. Expect roughly 10.3 wet days totalling 75.9mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Newmarket is May–September.
Based on BALDWIN, ON CA (26.9km), 1995–2024. 17 years of September data.