Photo/Illutration Mist offers a reprieve from the hot sun for pedestrians in Fukuoka on Aug. 1. (Kengo Hiyoshi)

Last month was the hottest July in Japan in more than a century, according to analysis by The Asahi Shimbun of average temperatures since 1898.

The temperature averaged 25.96 degrees for the entire month, exceeding the previous record of 25.58 degrees set in July 1978, the study found.

“August is the hottest month of the year in Japan, and the temperature is forecast to be higher than in average years,” a Japan Meteorological Agency official said. “We need to be more vigilant against the risk of heatstroke than in usual years."

The calculations were based on JMA daily average temperature data since 1898, when modern observation methods came into use.

In early July, daily averages were an unremarkable 24 degrees or thereabouts. But temperatures soared in late July as a sequence of typhoons passed the Philippines and a Pacific Ocean high-pressure system covered the Japanese archipelago.

The mercury often lingered above 26 degrees from around July 10 and reached unprecedented levels toward the end of the month, exceeding 28 degrees between July 25 and 31.

The JMA averages hourly temperatures at observation points across the country. It publishes the figure as a daily average for each location.

The Asahi Shimbun calculated the nationwide daily average based on data from 15 observation points and then arrived at the nationwide monthly average for July every year.

The JMA uses those 15 observation points as a basis for average temperature statistics because they are located away from urban hot spots, where asphalt pavements, vehicle engines and air conditioner vents tend to hike temperature readings.

The Asahi Shimbun made the calculations under the guidance of JMA experts.

The rise points to a long-term trend of global warming. Over the 126 years studied, July average temperatures have risen about 1.5 degrees. There was also a 1.8 degree increase during the first six months of the year.

But the increase has been sharpest in recent years. From the year 2000 onward there was a notable increase in the number of days with a maximum of at least 35 degrees.

Urban centers have it the worst. Data from Tokyo’s Chiyoda Ward, Nagoya’s Chikusa Ward, Osaka’s Chuo Ward and Fukuoka’s Chuo Ward showed a July average of 28.84 degrees, 2.3 degrees higher than in 1898.

The human toll is harder to measure, but heat stroke data give some clues.

Preliminary data from the Fire and Disaster Management Agency show 33,000 people nationwide were taken to the hospital with suspected heatstroke during the four weeks through July 30. The data refer to people transported in ambulances, for which the agency is responsible.

Finally, the year 2023 is not short of records. The average temperature for the first six months also set a new record of 12.14 degrees, surpassing the previous record of 12.02 degrees in 2020.

It was particularly warm in March. The average temperature was 10.36 degrees, the highest on record. The previous high was 9.99 degrees in 2021.

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