Today on June 3, multiple areas of Japan are expecting thunderstorms. The term ゲリラ豪雨, which directly translates into guerrilla heavy rain, is often used in weather reports to describe such incidents. It’s natural people affected by the rain tweet about it and cause the tag ゲリラ豪雨 to trend today.

The fun part happens when ゴリラゲイ雨 starts trending. This was actually not an existing term in Japanese, but a wordplay around the spelling of ゲリラ豪雨. Like this,

ゲリラ豪雨 (げりらごうう, GEH-RI-RA-GOH-U) -> ゴリラゲイ雨 (ごりらげいう, GOH-RI-RA-GEH-U)

The direct translation of ゴリラゲイ雨 is gorilla “GEH” rain, which sounds funny but also hints how extreme the weather is. One of the earliest tweet using this term can be dated back to this tweet by @mochilon in 2008. Since then this term often goes trending together with ゲリラ豪雨.