Castle Clinton National Monument in September
September at Castle Clinton National Monument averages a daytime high near 76°F and an overnight low around 62°F, with about 4.3" of precipitation. Visitation runs about 1× the park's average month, which makes September an average month here.
- Average low
- 62°F
- Average high
- 76°F
Range across the year: 28°F to 85°F
- Precipitation
- 4.3 in
- Daylight
- 12.3 hours
Roughly 8% of the park's yearly visitors come in September: about 323,000 recreation visits in a typical year, based on National Park Service monthly counts from 1979 to 2025.
That makes September the 7th-busiest of the park's twelve months, sitting between the July peak (1.6×) and the January low (0.5×).
September is our recommended month at Castle Clinton: pleasant weather with noticeably thinner crowds (shoulder season).
The daily average of about 69°F is a comfortable range for hiking and being outdoors all day. These figures are 1991–2020 NOAA climate normals from the nearest station, about 5.8 miles from the park.
Because June, July and August together draw about 37% of annual visitors, choosing September instead steps outside that summer crush — the single biggest lever on how crowded the park feels.
You'll have about 12.3 hours of daylight in September to explore — between the 9.1-hour midwinter low and the 14.9-hour summer high.
Park-wide, 2025 drew 3,656,350 recreation visits, down 4.4% from 3,822,759 in 2024.
Across the past decade overall visitation has eased about 28.2%, so September may feel a touch quieter than it once did.
How September compares with the months around it
| Month | Avg high / low | Crowds | Best-time score |
|---|---|---|---|
| August | 83°F / 69°F | 1.5× Busy | 44 Poor |
| September | 76°F / 62°F | 1.0× Average | 67 Good |
| October | 65°F / 51°F | 1.1× Average | 52 Fair |
All twelve months at Castle Clinton, with the best time to visit.
Frequently Asked Questions
September averages a daytime high near 76°F and an overnight low around 62°F at Castle Clinton National Monument, with about 4.3 inches of precipitation. These are 1991–2020 NOAA climate normals from the nearest station, about 5.8 miles from the park, so conditions inside the park can differ, especially at other elevations.
September is average at Castle Clinton National Monument (about 1.0× the average month). Our best-time score rates it "Good" at 67/100. September is our recommended month for this park.
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.
A typical September sees about 323,000 recreation visits at Castle Clinton National Monument, based on National Park Service monthly counts from 1979–2025.
Where to stay near Castle Clinton in September
Booking a September trip to Castle Clinton National Monument? Compare hotels, cabins and vacation rentals near the park with live September availability and prices.
Top-rated places to stay near Castle Clinton
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See the full ranking of the best national parks to visit in September.
Source: National Park Service Visitor Use Statistics (1979–2025), NOAA NCEI Climate Normals 1991–2020. Updated 2026-10-11.