What's the difference between 'Partly Sunny' and 'Mostly Cloudy'?

Partly sunny? Or Mostly cloudy? Sounds like the can be interchangeable but the National Weather Service has specific definitions on each term used to describe cloud cover.

Weather: Dreary and mostly cloudy

Partly sunny' vs. 'mostly cloudy': What's the difference?

Partly sunny and cloudy, chilly temps

Sunny Partly Cloudy Stock Illustrations – 1,394 Sunny Partly Cloudy Stock Illustrations, Vectors & Clipart - Dreamstime

We hope eclipse day is as sunny as it was Monday

Partly to mostly cloudy skies throughout the day with passing showers in the afternoon

Matt's Weather Spot: Partly Cloudy vs. Partly Sunny

Seattle FAQ News, Weather, Sports, Breaking News

Intro Guide Part One: Mostly Sunny vs Partly Cloudy – janesweather

What's the difference between partly cloudy and partly sunny?

Tim Leishman (@Leishman82) / X

Intro Guide Part One: Mostly Sunny vs Partly Cloudy – janesweather

Partly Cloudy vs Partly Sunny - Difference and Comparison