Guerilla rain season

One of the weather phrases I really love in Japan is "ゲリラ豪雨" which is read "gerira gou". The 'gerira' is from the Spanish word Guerilla, which we also use in English especially when referring to a member of an unofficial military group. Reportedly the word in Spanish literally means "small war". But in English we also use it to refer to impromptu, unauthorized actions. In Japanese, the word is used to describe rain that is unpredictable, sudden and aggressive.

Officially, for rain to be considered "guerilla", more than 100 millimeters falls in a localized area in just one hour. For the last three days in a row we have had guerilla rain here in Saitama Prefecture. Guerilla rain showers, although short, wreak havoc. Today's sudden downfall caused the Tobu Ogose line to stop suddenly due to too much rain on the tracks. Last night's news reported on several disruptions to rail services due to guerilla rain earlier that day. Roads also often need to close temporarily, especially ones that are sloped. 

On Monday night I was caught in a guerilla rain shower while driving. The rain was so violent that it created a river on the roads within seconds. It felt like 100 millimeters of rain was falling in just one minute, not one hour. Guerilla rain often brings thunder and lightning too, which it has done here for the last three days. The one and only positive of these type of rain showers is a temporary relief from the unbearable heat. However, on the flip side, a couple of hours after the showers are over, if the sun comes back out it creates a sauna effect making it even hotter than before. 

If you see cumulonimbus clouds gather and darken, there is a chance guerilla rain will follow. Thankfully, the guerilla showers usually don't last much more than an hour. However, during that time the rain is relentless and umbrellas pointless. It is best, if possible, to take shelter somewhere until the rain passes. Typhoons are on the horizon too... take care everyone!