Heavy Rain Along Japan’s Coast and Extreme Heat Disrupts the Tokyo Olympics

Heavy Rain Along Japan’s Coast and Extreme Heat Disrupts the Tokyo Olympics

This Post was submitted by Climate Scorecard Japan Country Manager Yun Tzu-Lin

In July, Japan suffered from heavy rain that caused devastating flooding and landslides, especially in the coastal city of Atami. As the Japan Meteorological Agency finds, this is part of a trend of increasingly frequent extreme weather events where the occurrence of rainfall in excess of 50mm per hour increased by 40% between 2010 to 2019 compared to 1976 to 1985. [1]

Additionally, Japan has experienced record-breaking temperatures during the summer in recent years, most notably the heat wave in 2018 that resulted in over 1000 deaths. While this summer’s heat waves were not as extreme, hot and humid weather resulted in more than 8,000 people hospitalized for possible heat stroke from July 19 to 25 alone. [2]

Japan developed its “National Plan for Adaptation to the Impacts of Climate Change” in 2015. It was based on the IPCC’s Fifth Assessment Report, projecting a 1.1 ℃ to 4.4 ℃ increase in average temperatures at the end of the 21st century as compared to the end of the 20th century. The plan includes sectoral measures such as facility improvements and hazard maps in coastal areas prone to natural disasters as well as disaster prevention functions of ports and harbors, railways, roads, etc. [3]

In particular, Japan took measures to relieve the amount of strain placed on athletes competing in outdoor venues at the Tokyo Olympics. Events such as the marathon and race walking were preemptively moved to the northern city of Sapporo in Hokkaido, where temperatures are significantly cooler [4]. At the beginning of July, the Ministry of Environment further unveiled a “Heat Stress Index for Surrounding Areas of Competition Venues” to rank on an hourly basis the heat threat at each Olympics venue with a five-step scale range from blue (almost safe) to red (danger).

Japan’s infrastructure, especially in rural regions, was unprepared to deal with the floods in July. The Japanese government ought to update its 2015 Adaptation Plan and increase its support towards formulating adaptation plans for different regions of the country.


The “Climate Change Adaptation Information Platform (A-PLAT)” is a portal that provides centralized information on the impacts of climate change to support the local governments in implementing adaptation measures. The platform can be reached at a-plat@nies.go.jp


[1] https://earthobservatory.nasa.gov/images/148616/heating-up-in-tokyo [2] https://edition.cnn.com/2021/07/30/sport/tokyo-2020-heat-weather-spt-intl/index.html [3] https://adaptation-platform.nies.go.jp/en/plan/national_plan.html [4] https://edition.cnn.com/2021/05/25/sport/olympics-heat-climate-change-spt-intl/index.html

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