Thanks, JamesM, for your version."Gust" is associated with wind in my mind, not rain. "Short bout" also sounds unusual to me. Some people do say "We have had a bout of bad weather" but I don't think of any individual event as a bout.
I would use "spell" before I would use "gust" or "bout".
There was a short spell of rain for half an hour in my part of the world.
Depending on the type of rain it could be one of many, many words. "Spell" doesn't tell us how heavy the rain was, only that it rained.
 As a side note, I certainly do find a large number of occurrences of "a bout of rain" using Google. I may be the odd man out here.
Thanks, soccergal, for the interesting and entertaining info.I'm with JamesM (sort of) Gust is definitely wind-related. I might say bout of rain, but only if I meant several rainy days, not a short period in one day. Spell is also something I would use for longer period of time, and I usually hear that in terms of no rain: dry spell.
Cloudburst is a short but heavy storm. Rain shower also signifies a short period of rain, not necessarily a storm.
But you can have scattered rain showers, and you can have showers off and on all day. Short rain shower makes the distinction that it came and went during an otherwise rain free day. I do wish you would tell my son that a shower, by definition, is short, but that is an entirely different matter.A shower is short, isn’t it? So you don’t need to say both; and you certainly don’t need to say half an hour at the same time. But you can say a half-hour shower. That’s different, and permissible.
And nice, too, because it rhymes.