The best cloud cover that I've found is yr.no

For example (and it always takes a bit for me to find it) https://www.yr.no/en/details/table/2-4887398/United%20States... (and https://www.yr.no/en/details/graph/2-4887398/United%20States... )

And here's their API - https://developer.yr.no/featured-products/forecast/

It breaks it down by overall, low, medium, and high clouds.

At the fringes, there is a meaningful difference. The center 50%, not really.

A 95% coverage day is a bit different than a 100% coverage day. Particularly, when it comes to rain and wind expectations.

How is that difference meaningful? What actions are you going to take differently at 95% cloud coverage vs 100%? I can't think of anything I'd do differently if I was expecting 100% cloud coverage tomorrow to wake up and find that it was actually at 95%.

Yeah, and I’d argue that if the difference is meaningful to you, then you probably want something more accurate than what a consumer-grade weather service can provide. So it would be borderline irresponsible of Apple to even give you the false confidence of some precise measurement of cloud cover.

in my experience its more like: 0-5% - Sunny; 5-60% - Partly Cloudy; 60-100% - Cloudy;

I've not seen other descriptors, and to view it changing over time its just on the timeline as a sun, sun+cloud & cloud emoji's

It's not useful other than as a binary 'is it cloudy' which in Bay Area weather it is a meaningful difference between 30% and 60% coverage

I would expect certain segments of aviation to find the additional granularity critical.

Presumably they shouldn’t be using a consumer weather service and mobile app.