Methodology
WhenToVisitParks answers one question for every U.S. national park unit: when should you actually go? We do it with public data only — no opinions, no sponsored placements — and we publish exactly how the numbers are built so you can judge them yourself.
Data sources
- Crowds — the National Park Service Visitor Use Statistics program, which publishes monthly recreation-visit counts for every reporting unit back to 1979. This data is in the public domain (CC0).
- Weather — the NOAA NCEI U.S. Climate Normals (1991–2020), matched to the nearest weather station to each park.
- Daylight — computed from each park's latitude using the standard sunrise equation (no third-party data).
The crowd index
For each park we average the last ten full years of monthly visits to get a typical seasonal curve, then express each month as a crowd index: the month's visits divided by the park's average month. A value of 1.0 is an average month, 0.5 means half as busy as usual, and 2.0 means twice as busy. Because the index is relative to each park's own baseline, it is comparable across a tiny monument and a marquee park alike.
The Best Time to Visit Score
Each month gets a 0–100 score combining three transparent, fixed-weight components:
- Crowd avoidance (40%) — quieter months score higher.
- Weather comfort (45%) — average temperatures near a comfortable ~68°F score highest, with penalties for heavy rain or snow.
- Daylight (15%) — longer days score higher.
The headline recommendation is deliberately not the warmest month, because the warmest month is usually the most crowded. Instead we surface the shoulder season: the month with genuinely pleasant weather but below-median crowds. When no clear shoulder month exists, we fall back to the best overall balanced score.
Coverage and known limitations
- We cover 385 NPS units — not just the famous 63 "National Parks." 297 have a nearby climate station for full weather scoring; the rest are scored on crowds and daylight.
- NPS counts "recreation visits," which approximate but do not exactly equal unique people.
- Crowd patterns describe a typical year. A specific holiday weekend, eclipse, or event can run far busier than the monthly average.
- A few remote units sit far from any weather station, so their climate figures are lower-confidence or omitted.
Updates
Crowd data refreshes annually when the NPS publishes the prior year's monthly figures; climate normals update on NOAA's decadal cycle. This page and every park page show their last-updated date. Data current as of 2026-06-20.