How Crowded Is Castle Clinton in September?
September is an average month at Castle Clinton National Monument, running about 1.0× the park's average month — roughly 8% of the year's visitors come in September. That puts it between the July peak and the January low. Overall our best-time score rates September as "Good" for a visit. Typical September weather averages a high near 76°F and a low around 62°F, with about 4.3" of precipitation. You'll get about 12.3 hours of daylight to explore.
Frequently Asked Questions
September is average at Castle Clinton National Monument (about 1.0× the average month). Our best-time score rates it "Good". The single best month overall is September.
The busiest month is July and the quietest is January. September sits at about 1.0× the park's average, or 8% of annual visitation.
Source: National Park Service Visitor Use Statistics (1979–2025), NOAA NCEI Climate Normals 1991–2020. Updated 2026-06-20.