How Crowded Is San Juan Island in December?
December is a quiet month at San Juan Island National Historical Park, running about 0.6× the park's average month — roughly 5% of the year's visitors come in December. That puts it between the July peak and the January low. Overall our best-time score rates December as "Fair" for a visit. Typical December weather averages a high near 46°F and a low around 37°F, with about 2.5" of precipitation. You'll get about 8.1 hours of daylight to explore.
Frequently Asked Questions
December is quiet at San Juan Island National Historical Park (about 0.6× the average month). Our best-time score rates it "Fair". The single best month overall is April.
The busiest month is July and the quietest is January. December sits at about 0.6× the park's average, or 5% of annual visitation.
Source: National Park Service Visitor Use Statistics (1979–2025), NOAA NCEI Climate Normals 1991–2020. Updated 2026-06-20.