Not a good night for stargazing in Rapid City, SD

Rapid City ranks 1st out of 500 US cities for night-sky darkness, with a darkness index of 100 out of 100. That estimate comes from the population of every community within 150 km, weighted by distance — so what matters is the glow of the whole metro area, not just the city's own size.

That puts Rapid City among the darker large cities in the country. On a clear, moonless night the Milky Way is often visible from the edge of town, and a short drive gets you genuinely dark sky.

Head away from major roads and shopping districts, and give your eyes about 20 minutes to fully adapt to the dark — most of what people call "bad seeing" is really just eyes that never adjusted.

Light pollution is the part that does not change night to night. Cloud cover and moonlight do, which is what the forecast above tracks.