In weather forecasts in the US, the phrase "a mix of sun and clouds" seems to be common whenever the forecast does not clearly predict rain or shine. In my recollection, forecasts used to have phrases like "partly sunny", "mostly sunny", and related variations "mostly cloudy", "partly cloudy".

My main question is, when did this transition occur? Google trends and n-grams don't tell.

I should probably stop there, but a second question nags me, which is, why? Granted, weather prediction is not an exact science, but the "mix" forecast seems like a cop-out.

P.s., if this question seems more suited to a more scientific channel I'm fine with that, but please consider I am firstly wondering about when the phraseology changed.

P.p.s., I am mostly thinking of media forecasts (particularly radio and TV). NOAA, from whom I suppose many of these outlets derive their forecasts, maintains the "partly sunny" etc. phrases.

  • To me the "mix" phrase implies a time-varying proportion, where as partly cloudy means the relative proportion of sun vs clouds is invariant over the day.
    – Oldcat
    Jun 25, 2014 at 0:29
  • In the UK it's usually variable cloud and clear spells these days when the weather is "unsettled". Overall, weather forecasts are now staggeringly accurate compared to just a few decades ago, so I seriously doubt they're deliberately using certain phrases as a "cop-out". Jun 25, 2014 at 0:35
  • @Oldcat I agree on the meaning, but my point is that "mix" did not used to be common, and now it is ubiquitous. Jun 25, 2014 at 0:36
  • It sounds like the NOAA has forgotten that it's meant to be a science-based organization. Earthly clouds cannot (presently) mix with the sun - the Earth and Sun are about 150 million Km apart. Any suggestions for what's next?
    – user63230
    Jun 25, 2014 at 0:38
  • 2
    I'm voting to close this question as off-topic because it could be better posed in Earth Science: Q&A for those interested in the geology, meteorology, oceanography, and environmental sciences
    – lbf
    Apr 14, 2018 at 16:26

3 Answers 3


"Partly cloudy," "partly sunny," "mostly cloudy," and "mostly sunny" are on a list of "General Forecast Terminology" published by NOAA.1 Each denotes a specific ratio of sun and clouds. These terms are by no means uncommon in weather reports today. "Partly cloudy" alone returns 22.2 million hits on Google, along with "partly sunny" at 2.8 mil, "mostly cloudy" at 11.9 million, and "mostly sunny" at 7.7 million.

"A mix of sun and clouds" is not a controlled term. It is also popular (38 million hits), but carries less of a precise ratio connotation.

Before asking why, we'd need to argue empirically in support of the historical trend, showing the decline of one term in preference for another over time. I don't see it in casual search engine queries.

  1. https://web.archive.org/web/20140627172513/http://forecast.weather.gov/glossary.php?letter=p
  • Your answer makes sense and gives good and helpful information. +1 for that!, but this does not answer the main question. The trend I am asking about might be difficult to measure because the media I am asking about are radio and TV. Also, the link drives to a "not found" page. Jun 26, 2014 at 1:45
  • Right. I am suggesting the trend might not be a trend. Fixed the link, thank you!
    – denten
    Jun 27, 2014 at 17:22

[Midwest US] - We have a couple of local weather guys (different stations) that forecast transitional/changing skies. Add that into the mix. A @denten points out some terms are used based on their area of expertise (weather lingo), but I am almost positive they just make stuff up. If they can't figure out the weather why would I trust them with English?

Transitional/Changing skies? I hope so or the Earth would have stopped.


Where I live in the San Francisco Bay Area, a day that is a mix of sun and clouds is likely to be sunny for a couple hours and then cloudy, or have some other alternate occurrence throughout the day (which is very typical). Partly cloudy would indicate to me that for the majority of the day, the sky would be partially obscured by clouds to some degree.

I can't cite a source for this usage, but logically it makes sense to me and conforms to my experience.

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