Napa, CA Night Sky Brightness
Napa, CA's night sky, measured from orbit
Satellite radiance puts Napa in the suburban edge band. A noticeable glow near the horizon. Brighter stars and constellations are easy to pick out; the Milky Way is washed out. That's brighter than 33.9% of the 3,206 US cities in this dataset.
Note the source: a satellite reading of upward light, not a visual Bortle scale reading. The two measure related but different things, explained in the Bortle scale guide.
How far Napa is from a meaningfully darker sky
The closest place in this dataset with a meaningfully darker sky is Benicia, CA, roughly 17 miles away in a straight line, rated rural. Road distance will be more.
Benicia, CA is itself still a measured city, not a designated dark-sky park, this only compares against the 3,206 places this dataset covers.
How Napa compares nationally
Napa, CA has a population of about 76,921, one of 3,206 US cities of 10,000 or more residents in this dataset. Napa's position, 1,081 of 3,206, darkest to brightest, comes from the sampling method the methodology guide sets out.