matek

>I wonder what the etymology is.

Yep, it's of Romance origin, etymological dictionaries list it as originating in Venetian nevèra, with an understandable semantic shift.

>Same thing?

I was commenting on the "short lasting" part (and the nuances between neverin vs nevera, first one being for "short lasting" storms/thunderstorms, the latter being more generic).

>The root of the word seems to be disbelief ne + vjera

The word is completely unrelated to disbelief, it's of Venetian origin (< nevèra, meaning snow blizzard).

>It’s a storm on the Croatian coast that comes suddenly and doesn’t last long

That would be neverin.

Nevera is a storm/thunderstorm in the Adriatic in general, not necessarily a short lasting one.