There Is a Reason for the Sweltering Heat... Tokyo's August Humidity Higher Than Bangkok's

Nikkei Reports
"Impact of Warming Seas Surrounding the Archipelago"

According to a report by Japan's Nihon Keizai Shimbun (Nikkei) on July 28, the average humidity in Tokyo during August over the past 10 years has been higher than that of Bangkok, Thailand.

Nikkei stated that over the past 10 years, Tokyo's average humidity in August has surpassed that of Shanghai, China, as well as Bangkok, which is located in a tropical climate zone. From the perspective of humidity, the perceived heat in Tokyo has now reached a level that exceeds even that of tropical regions during the rainy season.

On the 28th, a pedestrian is walking with a parasol on Asakusa Street near Sensoji in Tokyo. Photo by AFP

Hiroshi Takahashi, a professor at Tokyo Metropolitan University, told Nikkei, "The warming of the seas surrounding the Japanese archipelago is affecting the amount of water vapor." As the sea surface temperature off the coast of Japan has risen rapidly, a large amount of water vapor has flowed into the Japanese archipelago, resulting in Tokyo's humidity surpassing that of Bangkok. In fact, last August, the average amount of water vapor in the air (vapor pressure) reached an all-time high since observations began in Tokyo, Nagoya, and Fukuoka, while Osaka recorded the second highest level on record.

With not only temperatures but also humidity rising, the discomfort index?which quantifies the level of discomfort felt in hot weather?has also increased. Nikkei warned, "Temperatures across the Japanese archipelago are expected to be above average again this summer, and with sea surface temperatures remaining high, the extreme heat is likely to continue." The report also urged caution regarding heat-related illnesses such as heatstroke.

"Hokkaido Records 38.2 Degrees Celsius"

According to the Japan Meteorological Agency, June of this year was found to be the hottest month in Japanese history, and the average temperature for this month was also about 2.34 degrees Celsius higher than usual. Furthermore, the heat wave has intensified since July began. As of July 6, heat wave warnings were issued in 19 prefectures, including Tokyo, and temperatures in some areas exceeded 38 degrees Celsius.

Even Hokkaido, which is relatively cool, recorded its highest temperature since 1977, reaching 38.2 degrees Celsius on July 23. This heat wave in Hokkaido brought temperatures 12 to 13 degrees Celsius higher than average. The intense heat is expected to continue throughout this week in Japan. In particular, temperatures in cities such as Nagoya and Kyoto are forecast to reach as high as 39 to 40 degrees Celsius.