About VisitWhen
VisitWhen answers one question — "when should we go?" — with official data instead of guesses, for every US national park.
The National Park Service publishes monthly visitation counts for every park. NOAA publishes 30-year weather normals. Daylight is just math. Nobody had joined the three into a straight answer — so travel advice about timing stayed anecdotal ("summer is busy", "spring is nice") while the actual numbers sat in government databases.
VisitWhen computes the join: every month of every park scored by one public formula over crowds, comfort and daylight. When the data says a famous park is at 5% of its peak with hikeable weather, you'll see it. When "off-season" actually means the road is closed, you'll see that too.
VisitWhen is built and maintained by Caslon Media. It is not affiliated with, or endorsed by, the National Park Service or NOAA — we compute over their public data and always link the sources.
Who runs VisitWhen
VisitWhen is published by Caslon Media, the company of Paulo de Vries at Egelantiersgracht 424, 1015 RR Amsterdam (KvK 64708101, hello@caslonmedia.com). Paulo owns and runs Caslon Media and is responsible for what this site publishes. Questions or corrections: contact page.
How these pages are made
- Sources. Monthly visitor counts come from the NPS Visitor Use Statistics. Weather comes from the NOAA U.S. Climate Normals 1991–2020, from the nearest station, which each park page names. Seasonal closures come from each park's official NPS pages, and daylight is calculated from the park's coordinates.
- Writing. The text is drafted with AI assistance, working from those sources. The numbers are not written by the AI: every visitation figure, weather normal and month score is computed from the NPS and NOAA data by the formula on the methodology page.
- Checks. The build stops if any page would show an empty or broken value where a number belongs. The deploy stops if the NPS alerts shown on park pages are more than 14 days old, and the upload is refused if it would remove a tenth or more of the pages that are live.
- People. Not every page is read by a person before it goes live. That is why pages name their sources and show the date they were last checked.
- Corrections. If something is wrong, tell us on the contact page with the page address. We fix it on the page itself.
Paulo's name is not on individual pages: he runs the site but does not write each page himself.