Sources and method

Every figure on Park by Month comes from two federal data sets, processed by fixed rules. Nothing is written by hand for a single park.

Sources

  • Visitors: National Park Service, Visitor Use Statistics data package 2025 (CC0). Monthly recreation visits by park, averaged over 2023–2025.
  • Weather: NOAA National Centers for Environmental Information, U.S. Climate Normals 1991–2020, monthly, by station (public domain). Average daily high and low, total precipitation (rain plus melted snow) and snowfall. Precipitation and snowfall are separate measures: 10 inches of snow melts to roughly an inch of water.
  • Park locations: National Park Service Land Resources Division boundary centroids (public domain).
  • Daylight: worked out from each park's latitude for the 15th of the month, sunrise to sunset, with standard atmospheric refraction.

Method

  • Which parks: every national park, plus every other National Park System site averaging 50,000 or more recreation visits a year in 2023–2025, that has a NOAA station with full monthly normals within 60 miles of its centre (277 in all).
  • Weather station: the nearest such station to the park's center. Where a station within 40 miles sits 2,000 feet or more higher or lower, it is shown as a second station.
  • Weather words: average high above 90°F very hot, above 80°F hot, 55–80°F mild (mild, wet when that month's precipitation is above the park's median month), below 55°F cool, below 40°F cold.
  • Crowds: each month's visits as a share of the park's busiest month: 80% or more very busy, 55% busy, 30% moderate, below that quiet.
  • Best months: the mild months with the fewest visitors, up to three.

What the numbers can't tell you

These are long-term averages, not forecasts, measured at one or two points in parks that can span thousands of feet. They say nothing about road and trail closures, timed-entry reservations, fire restrictions or smoke. Each park page links to its official National Park Service page for those. Park by Month is not affiliated with the National Park Service.