More sweltering days forecast for September after hottest summer on record

 

More sweltering days forecast for September after hottest summer on record

By the end of August, 8,341 people had been transported by ambulance for heatstroke in Tokyo alone.

By the end of August, 8,341 people had been transported by ambulance for heatstroke in Tokyo alone. | AFP-JIJI

By Jessica Speed

STAFF WRITER

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Sep 1, 2025

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3 min

This summer was Japan’s hottest on record, with average temperatures nationwide more than 2.36 degrees Celsius higher than usual, according to a report released Monday by the Meteorological Agency.

The agency said this summer (June through August) was the hottest since records began, surpassing highs set in 2023 and 2024, when the deviation from the norm was 1.76 C in both years.

The agency attributed the heat to global warming and an unusually strong Pacific high pressure system, bolstered by convective activity in the Indian Ocean and around the Philippines.

Aug. 5 saw the hottest temperature in Japan on record, with the city of Isesaki, Gunma Prefecture, reaching 41.8 C. Of the 153 meteorological stations nationwide, 132 recorded their highest summer temperatures ever. The cumulative number of extremely hot days observed at weather stations nationwide this summer reached 9,385, surpassing the previous record of 8,821 in 2024.

Temperatures reached 38 C or above Monday in the town of Hatoyama in Saitama Prefecture and the cities of Nagoya, Tajimi, Kuki, Kiryu and Toyama in Aichi, Gifu, Saitama, Gunma and Toyama prefectures, respectively.

The extreme heat is expected to continue into September, with a one-month forecast released by the agency Thursday putting the probability of above-average temperatures for the month at 80% nationwide.

According to the report, temperatures are projected to remain high across the country through Friday, with an 80% probability of exceeding seasonal norms. The Tohoku and Hokkaido regions have a 70% chance of higher-than-average temperatures from Sept. 6 to 12, while other regions face an 80% probability. Elevated temperatures are expected to persist into late September and October, although with slightly lower probabilities.

The agency also expects there to be less precipitation and more sunlight across the country, though the western part of the Hokkaido-Tohoku region is expected to be rainier in September.

The most recent three-month outlook issued by the agency predicts above-normal temperatures across the country through November, driven by continued high sea surface temperatures near the Philippines and westerly winds flowing farther north than usual.

The hotter-than-average temperatures are also taking a toll on emergency services. By the end of August, 8,341 people had been transported by ambulance for heatstroke in Tokyo alone, surpassing last year’s record of 7,996, according to the Tokyo Fire Department.

The department is urging residents to take necessary precautions against heat exhaustion and heatstroke, such as using air conditioning, wearing hats or parasols outside to avoid direct sunlight, and drinking small sips of water before beginning to feel thirsty.