According to Springer, a cloud is an assembly of tiny water and/or ice particles in the atmosphere above the Earth's surface. Cloudiness or cloud cover refers to the extent to which the atmosphere is covered by cloud and is estimated in fractions or percent. Overcast refers to near 100% cloudiness while clear refers to near 0% cloudiness. The term cloudiness most often describes the horizontal extent of clouds, including all cloud altitudes as viewed from a weather station on the Earth or a satellite in space.
Latitude vs. Cloudiness shows no correlation between latitude and cloudiness across the 550 cities.