[garof]

They make a map for this: https://www.darkskymap.com/nightSkyBrightness

For the North American peeps, check out the western part of the US.

*edit: and forecasts https://www.cleardarksky.com/csk/

[bradknowles]

The astrophotography communities I am a member of tend to use the Bortle scale map at https://www.lightpollutionmap.info/

This one is more mobile-friendly, IMO.