In this particular map
from SkyVector, what are the meanings of the different colored circles, and for the different amounts of 'fill-in'?
- It's obvious by hovering over them, that they are weather stations, as the weather info will pop-up, but there doesn't seem to be anything (to my untrained eye) about the weather pop up that would indicate a need for the different colors.
- It's also obvious that the color doesn't indicate something permanent about the station, as last Friday, there were large swathes of different colors across the USA, while today almost everything is green.