Understanding Heavy Rain Warnings in Japan: Relatable Comparisons and Alert Criteria


In Japan, you often hear about heavy rain warnings and special warnings on the news, but it can be difficult to imagine just how much rain these warnings refer to. In this blog post, we’ll explain the amount of rain associated with warning-level heavy rain in Japan using easy-to-understand comparisons. We’ll also provide detailed information about the criteria for issuing these warnings to help you prepare for heavy rain events.


The Amount of Rain in Warning-Level Heavy Rain

In Japan, warning-level heavy rain refers to a situation where 80 millimeters or more of intense rain falls in one hour. To put this into perspective, it’s like having a full bucket of water dumped on you in just one hour. Additionally, if the daily rainfall exceeds 150 millimeters, there is an increased risk of landslides, and a special heavy rain warning may be issued.

Criteria for Heavy Rain Warnings in Japan

Heavy rain warnings in Japan are issued when it is predicted that 80 millimeters or more of intense rain will fall in one hour, or when the three-hour rainfall is expected to exceed 100 millimeters. Warnings may also be issued when continuous rain is expected to result in a 24-hour rainfall of 100 millimeters or more. It’s important to note that these criteria may vary slightly depending on the region, so it’s crucial to familiarize yourself with the specific criteria for your area in Japan.

Damage Caused by Heavy Rain and How to Prepare

Warning-level heavy rain in Japan can cause severe damage, such as river flooding, landslides, and inundation. When heavy rain is forecasted, pay close attention to evacuation information issued by local authorities and take action early. It’s also essential to prepare an emergency bag and confirm evacuation routes in advance.

Precautions During Heavy Rain in Japan

During warning-level heavy rain in Japan, avoid unnecessary outings. If you must go out, avoid flooded roads and stay away from swollen rivers. For those living in areas prone to landslides, take extra precautions and refrain from traveling near cliffs or steep slopes.


Warning-level heavy rain in Japan refers to a situation where 80 millimeters or more of intense rain falls in one hour, which is comparable to having a bucket of water dumped on you within that timeframe. To prevent damage from heavy rain, it’s crucial to prepare in advance and take appropriate actions when warnings are issued. Familiarize yourself with the warning criteria specific to your region in Japan and stay prepared for heavy rain events.