Meaning of “Guerrilla Gouu(ゲリラ豪雨)”

Guerrilla Gouu(ゲリラ豪雨)” means sudden heavy rain.
“Gouu(豪雨)” means heavy rain, and in this case, we use the word “guerrilla(ゲリラ)” as bringing unexpected sudden attacks, kind of.
Lately, this guerrilla gouu(ゲリラ豪雨) have become a common occurrence during the summer.
That’s why I don’t recommend visiting Japan in the summer. Not only is it extremely humid, but you may also be hit by sudden heavy rain.

Example Conversation

A: Yesterday’s guerrilla gouu(ゲリラ豪雨) was crazy!
B: I heard the trains stopped, too.
A: I even had a few short power outages at my place!

A: 昨日のゲリラ豪雨やばかったね。
B: 電車止まったらしいしね。
A: うちなんて何回か短い停電があったよ！