How Crowded Is Manhattan Project National Historical Park in December?

December runs about 0.5× Manhattan Project National Historical Park's average month, which makes it a very quiet month here — roughly 4% of the park's yearly visitors come in December.

In a typical December the park sees roughly 2,500 recreation visits, based on National Park Service monthly counts from 2016 to 2025.

That makes December the 10th-busiest of the park's twelve months, sitting between the July peak (1.7×) and the January low (0.3×).

On our Best Time to Visit score December rates 38/100 ("Poor"), versus the top-rated May at 56/100 — pleasant weather with noticeably thinner crowds (shoulder season).

Typical December weather, from 1991–2020 NOAA climate normals at the nearest station, averages a daytime high near 40°F and an overnight low around 21°F, with about 0.9" of precipitation and roughly 8" of snow.

That average of about 31°F is cold, with winter conditions likely on higher ground.

Because June, July and August together draw about 37% of annual visitors, choosing December instead steps outside that summer crush — the single biggest lever on how crowded the park feels.

You'll have about 9.6 hours of daylight in December to explore — near the year-round minimum.

Park-wide, 2025 drew 56,390 recreation visits, down 24.5% from 74,693 in 2024.

Across the past decade overall visitation has eased about 43.1%, so December may feel a touch quieter than it once did.