It takes a lot more than just the latitude, but we can make a very accurate prediction. I once worked on internal modeling software for doing precisely that, an

It takes a lot more than just the latitude, but we can make a very accurate prediction. I once worked on internal modeling software for doing precisely that, and IIRC our target was being within ~1% over a 10-year period (there's a bit of year-to-year variation depending on weather). Those numbers generally aren't released publicly though (because everyone wants to talk about the much bigger nameplate number), and at least as of five years ago the freely available tools for doing similar calculations were much less accurate.