How many clear nights a year?

How we count

A night counts from the moment the Sun is 8° below the horizon (bright stars are visible) until it climbs back. An hour is clear when cloud cover is 30% or less. A night is clear when at least 3 of its dark hours are clear (or 60% of them on short summer nights). Past years come from the ERA5 weather archive via Open-Meteo, recent nights are added every day. You can use this data with a link to NightSkyCast (CC BY 4.0): /api/db/rank, /api/db/city?s=vilnius