Whats the Difference Between Mostly Sunny and Partly Cloudy?

'My' forecast, now, for tomorrow, Calvert County, is 'partly cloudy' from 1 - 10 p.m. (AFTER 'scattered t'storms' @ noon!)

'“What’s the difference between ‘mostly sunny’ and ‘partly cloudy’ (or for that matter, ‘mostly cloudy’ and ‘partly sunny’) in weather forecasts? Are any of those even specifically defined terms?”

The short answer: about 1 to 4 oktas. What’s an okta? That’s a unit of measurement that meteorologists use when they’re forecasting cloud conditions, equal to 1/8 of the sky (though sometimes 1/10 is used). When the forecast is delivered, the number of oktas covered by opaque clouds (meaning that you can’t see through them, and the sun/moon/stars/sky are hidden) is described using “mostly sunny,” “partly cloudy” and other terms we’re used to hearing. Each of these is defined by the National Oceanic and Atmospheric Administration and the National Weather Service in terms of oktas of cloud cover. The NWS Operations Manual breaks it down like this:'>>>

http://mentalfloss.com/article/56820/whats-difference-between-mostly-sunny-and-partly-cloudy