In the course of planning a rather significant event for the coming weekend, I was forced, for the first time in my life, to confront the following conundrum:

Which is sunnier — “partly sunny” or “partly cloudy”?

My faith in the power of pure reason was severely shaken when I realized I could construct equally plausible arguments in either direction. So, with reluctance, I abandoned theory and turned to evidence, in the form of the logos employed by two of the more popular weather forecasting sites:



Weather Underground Accuweather Partly Sunny Partly Cloudy

Weather Underground takes an unambiguous stand: partly cloudy is definitely sunnier than partly sunny. Accuweather is a little, umm, hazier on the issue; apparently at Accuweather, partly cloudy means something like “somewhat wispier clouds, covering more of the central portion of the sun but a bit less of the edges, than partly sunny”. Overall, though, it appears that at Accuweather, partly sunny is sunnier than partly cloudy.

I turned to The Weather Channel to break the tie, but as far as I can tell (after checking ten-day forecasts for a half dozen cities), the melancholy folks at The Weather Channel are quite incapable of ever seeing the world as “partly sunny”. “Partly cloudy” they use with reckless abandon.

I invite commenters to weigh in both descriptively and prescriptively on this issue—what do “partly sunny” and “partly cloudy” usually mean in practice, and what ought they mean? If we succeed in resolving the matter, we can tackle the even more difficult question: