How Crowded Is San Juan Island National Historical Park in September?

September runs about 1.4× San Juan Island National Historical Park's average month, which makes it a busy month here — roughly 12% of the park's yearly visitors come in September.

In a typical September the park sees about 48,000 recreation visits, based on National Park Service monthly counts from 1979 to 2025.

That makes September the 4th-busiest of the park's twelve months, sitting between the July peak (1.8×) and the January low (0.5×).

On our Best Time to Visit score September rates 54/100 ("Fair"), versus the top-rated April at 61/100 — best overall balance of crowds, weather and daylight.

Typical September weather, from 1991–2020 NOAA climate normals at the nearest station, averages a daytime high near 68°F and an overnight low around 48°F, with about 1" of precipitation.

That average of about 58°F is a comfortable range for hiking and being outdoors all day.

Because June, July and August together draw about 42% 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 8.1-hour midwinter low and the 15.9-hour summer high.

Park-wide, 2025 drew 420,922 recreation visits, up 3.7% from 405,925 in 2024.

Across the past decade overall visitation has risen about 68.5%, so a September visit is likely to feel busier than it did a few years ago.