I regularly get Sunny-16 in Australia, even when it's not summer. I found though that Europe (Prague and St Petersburg) was metering at about f/13 so I have a bunch of slides that are about half a stop dark. And even slight haze of high-level cloud will reduce the visible light here to f/11.

For a quick comparison of daylight (and UV) intensities, consider that you can spend a day in full sun in Europe with little or no effect, maybe the beginning of a tan and a bit of warm feeling in the cheeks. In Australia, that "warming" takes 10 minutes; an hour will get you a painful burn, 4 hours will burn you bad enough that you can't sleep and 6 hours will require hospitalisation. So there are definitely geographical differences in sunlight intensity, especially if you want to shoot (UV-sensitive) alt processes.