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Last updated: Sun. May. 25, 2014 - 08:41 am EDT


The forecast: a 100 percent chance of partly cloudy weather lingo

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Flipping through channels the other day, I came across a weather forecast on, of all places, The Weather Channel.

Yes, somewhere between “Strangest Weather on Earth,” “Storm Stories,” “Tornado Hunt” and all its other weather-related programming, TWC managed to squeeze in an actual forecast. This renews my faith that someday I might actually see another music video on MTV or learn something on The Learning Channel.

Among the phrases you hear in just about every forecast are the somewhat mysterious “partly cloudy,” “mostly cloudy,” “partly sunny” and “mostly sunny.” Have you ever been perplexed by exactly what the difference is between all of those terms? As a public service, I asked my meteorologist daughter — who, unfortunately, is not named Lucy — to ’splain something to me.

Dumbed down so even I could understand it, here are the official National Weather Service guidelines:

Sunny or clear: When no opaque clouds exist at all. Obviously, the term “sunny” is used only during daylight hours. (Unless you are in Philadelphia, where “It’s Always Sunny ...”).

Mostly sunny: When 1/8 to 1/4 of the sky is covered by clouds. At night, the same conditions are considered “mostly clear.”

Partly sunny or partly cloudy: Between 3/8 and 5/8 of the sky is covered by clouds. Again, the term “partly sunny” is used only during daylight hours.

Mostly cloudy: When 3/4 to 7/8 of the sky is covered by clouds.

Cloudy: When 7/8 or more of the sky is covered by clouds.

As you can see, a fine line divides many of these terms. Add to that the constantly changing atmospheric conditions that make pinpoint forecasting virtually impossible, and you can see why meteorologists coined the phrase “50 percent chance of ...”

Mike Marin is a cranky curmudgeon who, when hes not yelling at kids to get off his lawn, likes to complain about the sad state of popular culture, especially as seen through a TV screen. His email address is This column is the personal opinion of the writer and does not necessarily reflect the views or opinion of The News-Sentinel.

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