Notifications - at the bottom of the screen "Manage Notifications". Enable "Next-Hour Precipitation". It is off by default since it leaks data back to Apple. https://imgur.com/CwlFnym

The precipitation graph you get when you expand the perception tile. You can then scroll through the days. Here's a screen shot from my phone for a couple days from now when I'm due to get some snow. https://imgur.com/FnWdQ4b

I don’t have that graph.

Probably yet another feature locked to the US. At this point it is ridiculous that iPhones outside the US don’t come with a 5% ‘reduced service’ discount.