Cloud cover
Also called: low cloud, mid cloud, high cloud, cirrus.
How much of the sky is covered by cloud, split into low, middle and high layers.
Low cloud (below about 2 km) and middle cloud are thick and block everything. High cloud — thin cirrus — is often barely visible at night but dims faint objects and brightens the sky, so it's worse than it looks for deep-sky observing.
In AstroPilot
AstroPilot forecasts cloud at all three heights, hour by hour, and shows a cloud map with satellite images and the week's forecast.