Record-Hot September Marked in Japan, Hot on the Heels of Hottest July and August

The Yomiuri Shimbun

6:00 JST, October 4, 2023

Last month was the hottest September on record in Japan, the Japan Meteorological Agency announced on Monday. The “temperature anomaly,” a measurement of how much the temperature differed from that seen in an average year, was plus 2.66 C in September, much higher than the plus 1.51 C marked in 2012 and making it Japan’s hottest September since statistics began in 1898.

This was the third consecutive month in which the temperature anomaly hit a record, following a record-hot July and a record-hot August.

By region, the temperature anomaly in the Tohoku region was 3.4 C, the highest among all regions, followed by 3.3 C in the Kanto-Koshin region and 3.2 C in the Hokuriku region. Of the 153 locations in Japan with temperature statistics for the past 50 years or more, 101 locations set new record highs for average temperatures in September.

This is believed to have been influenced by high-pressure systems in the Pacific Ocean hovering near Japan to the southwest and record-high sea surface temperatures around the archipelago. Due to hovering high-pressure systems in the Pacific Ocean, the number of typhoons that formed in September stood at only two, which was the lowest on record, matching the September number seen in 1951, 1973 and 1983. In an average year, the number of typhoons forming in September is five.

Temperatures in October are also expected to be higher than average nationwide.