The National Weather Service says:

What is the difference between "Partly Sunny" and "Partly Cloudy"? The forecast, as written by the National Weather Service, always contains the sky condition, such as "clear" or "mostly cloudy", as one of the required weather elements. The sky condition term is based on the number of tenths of opaque cloud cover expected during the forecast period (e.g. "today" or "tomorrow night"). A forecast of "Cloudy" expects the sky, on average, to be covered with 9/10 to 10/10 of opaque cloud cover. "Opaque" clouds block the sun, unlike thin cirrus, which lets most of the sun, and its heat, through to the ground. A forecast of "Clear", however, expects the sky to be covered with 0/10 to 1/10 of opaque clouds. A forecast of "Partly Cloudy" or "Partly Sunny", is made when between 3/10 and 6/10 of the sky is to be covered with clouds. The difference between these terms is based on the forecast period itself - during the day, either term could be used. However, for the nighttime forecast periods, a forecast of "partly cloudy" would be the only appropriate term, as there is no sunshine at night!

Excellent reply!

Partly Sunny:

• Indicates more sunshine than clouds.
• Typically used during the day.
• Suggests a generally pleasant weather experience.

Partly Cloudy:

• Implies more clouds than sunshine.
• Can be used at any time of day.
• Often indicates a slightly less favorable weather condition compared to partly sunny.

Elmer, if I could have just a dollar for each time he made me laugh, including the hippy dippy weatherman!

I miss him.

I think there were different versions of his Hippy Dippy weather reports. I remember one when he was standing in front of a map holding a pointer and said

"We have various conditions that will be influencing us in the coming hours. Don't confuse a Canadian low with a Mexican high. "

There are some videos of his performances on YouTube and I'll watch him when I feel like I need a laugh.

A forecast of "Partly Cloudy" or "Partly Sunny", is made when between 3/10 and 6/10 of the sky is to be covered with clouds.

Glass half empty or half full?

Partly Cloudy = Mostly Sunny

Partly Sunny = Mostly Cloudy

Carlin’s humor has remained amazingly pertinent. Wouldn’t he have been brilliant in today’s political environment?

I’d have interpreted as vgkg wrote, but that’s opposite of what jrb wrote. I guess I’ll make it wasy and follow what NWS says.

I'd prefer "partly sunny," because most weather announcers today say "partly cloddy". So grating!

In coastal New England, it’s ”Partly Clammy.”