How Crowded Is Manhattan Project National Historical Park in May?

May runs about 1.2× Manhattan Project National Historical Park's average month, which makes it a busy month here — roughly 10% of the park's yearly visitors come in May.

In a typical May the park sees roughly 6,500 recreation visits, based on National Park Service monthly counts from 2016 to 2025.

That makes May the 6th-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 May rates 56/100 ("Fair") — the single best-rated month at Manhattan Project, balancing crowds against weather and daylight.

Typical May weather, from 1991–2020 NOAA climate normals at the nearest station, averages a daytime high near 70°F and an overnight low around 44°F, with about 1.2" of precipitation.

That average of about 57°F is a comfortable range for hiking and being outdoors all day.

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

You'll have about 13.9 hours of daylight in May to explore — between the 9.6-hour midwinter low and the 14.4-hour summer high.

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 May may feel a touch quieter than it once did.