ROCHESTER, N.Y. (WROC) — In the world of weather, there are a number of phrases used to describe the varying degrees of cloud cover in the sky. Some include sunny, mostly sunny, partly cloudy/sunny, mostly cloudy, cloudy, and overcast.
Each one of these phrases describes a percentage of how much cloud cover is present in the sky whether it’s 0% or 100% covered. There is more than one way to describe these percentages, but for now we’ll stick with the phrases cloudy versus overcast skies.
To some people the difference between cloudy and overcast is the same, and it’s not wrong. They are both accurate ways to describe the fact that the sky is nearly if not completely covered in extensive clouds, but to a meteorologist the difference can be broken down even further.
A cloudy sky is typically one in which clouds dominate over the sun during the day, or obscure the stars at night. There may be breaks in the clouds where you catch fleeting glimpses at either blue or dark skies, but for the most part the sky is covered.
An overcast sky is usually saved to describe a sky that is 100% and completely covered in clouds with zero breaks in between. This is usually composed of widespread, uniform gray clouds that sit fairly low in the sky such as a deck of stratus or nimbostratus.
COMPARE IT TO:
Think of overcast like a blanket that completely covers you with no holes or spaces like the green one shown below. Then think of cloudy like a quilt or blanket that’s knitted with tiny holes in it, but it still covers you fully like the top and bottom ones below:
The National Weather Service uses both cloudy and overcast to describe a sky that’s 88-100% covered in clouds. Check out their definition of average sky conditions below:
Since these terms refer to a mostly cloud covered sky, both can be used and be correct for the most part.
~Meteorologist Christine Gregory