United States · International Dark Sky Park
Stargazing at Mammoth Cave National Park
How dark this certified sky really is, how far it is from the nearest cities, a live seven-night forecast for the site itself, and the moon-free nights worth planning around. Official DarkSky International page ↗
How dark the sky really is at Mammoth Cave National Park
Modelled zenith brightness at the site's coordinates is 21.25 mag/arcsec², which maps to roughly Bortle 4 (what each level means). This is an approximation from the 2024 light-pollution atlas, not a field measurement — and it describes the single point DarkSky lists, not the darkest corner of the park.
Rural-to-suburban transition: the Milky Way is clearly visible on clear, moonless nights, though light domes from nearby towns sit on parts of the horizon. Certification here is as much about the international dark sky park's lighting policy and public programmes as about raw darkness — aim your observing away from the brighter horizon.
Getting to Mammoth Cave National Park
The nearest cities we publish guides for, with the direction to head and a rough drive estimate.
- From Nashville
head north-east · 129.2 km straight-line · ≈168 km by road · ≈2.2 h · weekend trip
- From Atlanta
head north · 412.2 km straight-line · ≈535.9 km by road · ≈6.1 h · weekend trip
- From Chicago
head south · 538.2 km straight-line · ≈699.7 km by road · ≈7.8 h · weekend trip
Estimated from straight-line distance x a 1.3 road-detour factor and staged average speeds (40 km/h leaving town, 70 km/h regional, 95 km/h highway). It is a rough guide, not a routed drive time.
The next seven nights at Mammoth Cave National Park
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Plan the next 90 days at Mammoth Cave National Park
Moon-free dark windows are astronomy — computable years ahead. Cloud is not: beyond the 16-night forecast nobody knows the weather, and we won't pretend to. What five years of reanalysis can say is how often each month's nights actually stayed clear here.
- Nov 2–1514 moon-free nights53% of November nights here stayed clear (2021–2025)
- Dec 2–1413 moon-free nights34% of December nights here stayed clear (2021–2025)
- Dec 31 – Jan 1314 moon-free nights34% of December nights here stayed clear (2021–2025)
Clear nights by month, 2021–2025
- Jan37%
- Feb44%
- Mar51%
- Apr53%
- May53%
- Jun68%
- Jul67%
- Aug79%
- Sep79%
- Oct72%
- Nov53%
- Dec34%
Clearest months historically: August (79%), September (79%), October (72%); across the year 58% of nights with astronomical darkness stayed clear.
"Clear" = weighted cloud cover (low 0.5 / mid 0.3 / high 0.2) ≤ 20% across the night's astronomical darkness. ERA5 reanalysis via Open-Meteo Archive, 2021–2025 (CC BY 4.0) — historical frequency, not a forecast. Once a window comes within 16 nights, the live forecast above takes over.
Put Mammoth Cave National Park's dark-sky nights on your calendar
Every month has a stretch of nights when the Moon leaves the dark hours at Mammoth Cave National Park essentially moon-free. Subscribe once and each window lands in your own calendar, about a year ahead — no account, no email.
moon & darkness geometry only — cloud can't be known this far out; check the live forecast above when a window gets close
Questions people ask about Mammoth Cave National Park
- How dark is the sky at Mammoth Cave National Park?
- Modelled zenith brightness from the 2024 World Atlas of Artificial Night Sky Brightness puts Mammoth Cave National Park at about 21.25 mag/arcsec², roughly Bortle class 4. That is an approximation derived from satellite data, not a field measurement; it is certified by DarkSky International as an International Dark Sky Park.
- How far is Mammoth Cave National Park from Nashville?
- About 129.2 km in a straight line, heading north-east from Nashville. Using a 1.3 road-detour factor and staged average speeds that is roughly 168 km and 2.2 h of driving — an estimate, not a routed drive time.
- When is the next moon-free dark window at Mammoth Cave National Park?
- The next stretch of essentially moon-free dark hours runs Nov 2–15 (14 nights), computed from Moon phase and altitude with Skyfield and JPL DE440s. Cloud cannot be known that far ahead; the live seven-night forecast on this page shows real cloud cover once a window is close.
- What is the clearest month at Mammoth Cave National Park?
- Over 2021–2025, August (79%), September (79%), October (72%) had the highest share of nights with astronomical darkness that stayed clear (weighted cloud cover ≤ 20%); across the year it was 58%. ERA5 reanalysis via Open-Meteo — historical frequency, not a forecast.
Place name and coordinates: DarkSky International (reviewed 2026-07-15, data 2026-10-13). Light pollution: David Lorenz, World Atlas 2024 (EOG VIIRS, CC BY 4.0), approximate. Cloud: Open-Meteo.com (CC BY 4.0). Moon and darkness geometry: Skyfield + JPL DE440s, computed locally. Drive times are estimates, not routes.