Taiwan has emergency messages, though not _that_ high frequency. There the main topics involve:

- earthquakes: these can arrive indeed before you even feel them (a few seconds before); they filter it to areas where it's expected to be felt, there are discussions around how sensitive to make it (how wide area it should cover)

- extremely heavy rain: this was new recently, and very useful, when locally it all went cats & dogs, more than maybe I've ever seen. See an example here: https://fosstodon.org/@imrehg/117058657161401667

- military drills: the yearly "if there's an invasion drill", they had sent reminder a week before, and then at the start/end; example here: https://fosstodon.org/@imrehg/117030180601973598

- Chinese rocket launches that will fly over the island (not sure what could one do about it, and never seen anything, so maybe this is more borderline)

Interestingly (for me), the headers seems to change over time. Started with "Presidential Alert", there were "Government Alert" then, now "Emergency Alert" and just "Alert". I'm not sure if there area list of these or it evolved over time...