Summer 2026 Was 1.2°C Above Average in Northern and Western Japan; Western Japan Saw Its Hottest 10-Day Periods Since 1946 in Mid- and Late July and Late August

Explanation

The Japan Meteorological Agency published a summary of this summer's (June–August) weather on September 1, 2026.

Looking at the difference from the average summer temperature (the 1991–2020 average), Northern Japan was +1.2°C, Eastern Japan was +0.8°C, Western Japan was +1.2°C, and Okinawa/Amami was 0.0°C. Looking at the three-month average, no region set a new record, so in that sense it was not as record-breaking a summer as last year.

However, the picture changes when the period is divided into 10-day intervals. In Western Japan, the average temperatures for mid-July, late July, and late August were the highest since records began in 1946. "Extremely hot days," with a maximum temperature of 40°C or higher, were observed in Tokai, Shikoku, northern Kyushu, and Kinki. The three-month average fell short of a record because hot and less-hot periods alternated, even though the peak heat itself was the highest on record.

Rainfall varied greatly by region. In the Kanto-Koshin region, precipitation reached 141% of the average due to the effects of Typhoons No. 6 and No. 15, among others, and the torrential rain that hit Chiba Prefecture in late August was named the "Reiwa 8 August Chiba Torrential Rain."

It is difficult to say in a single number whether the summer was hot. Looking at the three-month average, some regions were close to normal; looking at 10-day periods, records were broken; looking at individual days, temperatures exceeded 40°C. The answer changes depending on which period is used for the average.