Methodology — how every verdict is computed

Every month of every park gets a 0–100 score from one fixed, public formula: score = 0.45 × comfort + 0.35 × quietness + 0.20 × daylight, with an access penalty where a park's headline access is typically closed. No editors, no sponsors, no exceptions.

The data

Crowds — NPS Visitor Use Statistics

Monthly recreation visits per park from the National Park Service's official IRMA statistics service. We use the mean of 2021–2025 (five full years; 2020 is excluded as a COVID-19 anomaly). "Quietness" for a month = 100 − that month's percentage of the park's peak month.

Weather — NOAA climate normals

Monthly temperature and precipitation normals from the NOAA/NCEI U.S. Climate Normals 1991–2020, using the nearest station to each park's coordinates that has complete monthly temperature and precipitation normals. Every park page names its station and the distance — mountains create microclimates, so treat the station's numbers as the reference point, not gospel for every trailhead.

Daylight — computed astronomy

Daylight hours are computed for the 15th of each month at each park's coordinates using the NOAA solar declination series and the standard sunrise hour-angle equation (−0.833° refraction). Deterministic math, unit-tested against known invariants (equatorial ≈12h, polar day/night).

Seasonal access — curated from NPS

For parks with major seasonal closures (Going-to-the-Sun Road, Tioga Road, Isle Royale's full winter closure, Denali's bus season…), we curate typical open/close windows from each park's official NPS pages. Months where headline access is typically closed lose 25 points and can never be labeled "Best window."

The formula

Comfort (45%): starts at 100; graded penalties for heat above 80°F daytime highs (steeper past 100°F), cold below 58°F highs, nights below 28°F, and monthly precipitation above 2.5″.

Quietness (35%): 100 − crowd %-of-peak, from the NPS monthly averages.

Daylight (20%): hours normalized between 7h (0) and 15h (100).

Labels: Harsh season if comfort < 35 · Best window for the top-3 scoring months (≥55, accessible) · Peak crowds at ≥70% of peak · Shoulder otherwise.

Honest limitations

Normals are 30-year statistical averages — any given week can differ wildly. Crowd data counts park-wide recreation visits, not per-trailhead congestion. Station weather ≠ summit weather. Access windows shift year to year with snowpack; always check the park's live NPS alerts before booking. Where data is missing we say so — nothing on this site is invented.

Questions about the method? Contact us. Last verified 2026-07-16