"Mae hi'n bwrw cesair."
Translation:It is hailing.
Is bwrw cesair a southern thing? I grew up in the north and I've never heard that word! I'd call it cenllysg.
Yep, cesair is southern, cenllysg is northern. When you hear a weather forecast in Welsh, the word the forecaster uses will change depending on where they're from!
Bwrw is usually "to hit/strike". It has another meaning which is "to throw/cast/hurl" which isn't much used today, but that seems to be the idea with precipitation: Mae hi'n bwrw eira/glaw/eirlaw/cesair "It's casting snow/rain/sleet/hail". I seem to remember Manx has the same idiom: T'eh ceau sniaghtey/fliaghey/fliugh-niaghtee/sniaghtey garroo.
Would it be used for "casting a magic spell" (e.g. in fantasy stories and legends) as well?
There are a number of options that can be used for "cast a spell":
hudo "conjure, enchant, beguile"
swyno "charm, bewitch"
rheibio "bewitch, curse, beguile"
And as you guessed, there's the idiom:
bwrw hud ar lit. "cast magic on"
Thanks! That really makes a lot of sense to me, as "bad weather" quite often is blamed on someone bad for casting the spell (and magic is quite often a part of Welsh legends). I like it when languages make sense - and Welsh does, over and over again! :-D
Duo is not handling <'s> very well at the moment; it sometimes interprets it as being 'It has...' even where that makes no sense in English, as in * 'It has hailing', and offers that up as a valid alternative answer. We have to avoid giving it as an answer until Duo fix the bug.