Yes, there are! It can be used as an adjective in a non-military context The word 'guerrilla' has two definitions in the Free Dictionary. The first is the military one, and the second is this: referring to actions or activities performed in an impromptu way, often without authorization. adjective: guerrilla The example given in the dictionary is "guerrilla gigs", where a band suddenly stage a performance - in a shopping mall or park for example - without any warning. The 'surprise' element is part of the appeal.

There is a term “guerilla theater” which seems related to that which Su.Ki describes. I would not say however that “guerilla” is used in daily life, and certainly not regarding rain. For that I might say something like “local downpour” or “localized downpour”.

@Peter @Steven Thank you very much for your comments. The Japanese words, 'guerilla pouring' has been used for recent ten or fifteen years since the climate changing occurred. People in Japan often suffer from such unexpected landslide by pouring. It's sad and the usage of the word, 'guerrilla' makes a point to attack people., I think. Then, I 'm curious if there are similar sitations in English apoken countries.

There are a lot of words for different kinds of heavy downpours in Scottish Gaelic, but I don't know so many in English! In English, 豪雨 would be called "torrential rain", but ゲリラ豪雨 would be "a sudden burst of torrential rain" (a "burst" of rain = a sudden downpour). I have never heard the word "guerilla" used for anything other than in a military context - guerilla warfare, guerilla army, etc. therefore Su Ki's "Guerilla Gigs" is a new term for me!

No there aren't.