Q: What’s the difference between a forecast that says cloudy and one that says overcast?
A: There is a difference, says Brent McRoberts of Texas A&M University. The terms are based on weather definitions used by various agencies and organizations around the world. “There are different degrees of cloud cover – that’s the basic premise. General use of the word ‘cloudy’ implies there will be more clouds than sunshine,” McRoberts states. “More specifically, a forecast of partly cloudy expects a sky to be about 40 to 70 percent full of clouds, whereas a forecast of mostly cloudy anticipates about 70 to 90 percent of the sky to be cloud covered.”
Q: What does overcast mean?
A: Overcast means the entire sky is cloud covered, he adds. “An overcast sky is usually a dull and gray-looking sky when clouds are expected to cover all of the surrounding area. Many people just want to know if it’s going to be a sunny or a cloudy day. But for people like photographers, film makers and even pilots, the degree of cloudiness can be a crucial bit of information.”
Weather Whys is a service of the Department of Atmospheric Sciences at Texas A&M University.