Japan is experiencing another tortuously hot summer, with human-induced climate change driving up temperatures even in Hokkaido, where many people are not acclimated to heat.

Authorities are calling for utmost precaution as heatstroke alerts are being issued in 28 prefectures, from Hokkaido to Kyushu, for Friday.

On Thursday, the mercury hit 39 degrees Celsius in Kitami, a city in eastern Hokkaido, at around 2:30 p.m. ¡ª a record high ¡ª and 13.5 C above a 30-year average.

Obihiro, an inland city, recorded a temperature of 38.8 C, tying with the previous high observed in 2019.

The town of Rikubetsu, which bills itself as ¡°the coldest town in Japan,¡± also registered the highest-ever temperature of 36.6 C on Thursday.

The impact of the heat waves is huge, as Hokkaido, which has long prided itself on its cool and comfortable summer, is not used to handling extreme heat.

Air conditioners are selling like hot cakes but are still installed in only about 60% of homes in the northernmost prefecture, while the national average is 94.4%, according to a survey of about 12,000 people conducted this week by private-sector forecaster Weathernews.

On Thursday and Friday, Hokkaido Railway, or JR Hokkaido, suspended portions of lines connecting the stations of Kushiro and Sapporo as well as Abashiri and Kamikawa in the prefecture out of safety concerns. Extreme heat is known to cause the warping of rails.

The ongoing heat wave ¡ª driven mostly by the extension of the Pacific high-pressure system toward the nation ¡ª is gripping the rest of the nation as well, damaging crops and raising the number of heatstroke patients.

Analysis by U.S. nonprofit Climate Central shows that climate change¡¯s effects are prominent in the rise in nighttime temperatures.

On Thursday, many parts of Japan experienced nettaiya (tropical night), defined as nights when the lowest temperatures do not fall below 25 C. Authorities recommend people turn their air conditioners on at night and keep themselves hydrated by drinking water before hitting the hay and after waking up.

Climate change has made recent rises in the lowest temperatures ¡°at least five times more likely¡± in much of Japan, including the Tohoku, Kanto, Chubu and Kansai regions, according to data by Climate Central, which provides .

With the Tibetan high-pressure system some 10,000 kilometers above ground extending eastward, temperatures are predicted to remain high through next week.

On Tuesday, places such as Nagoya, Gifu and Kyoto are expected to see temperatures rise to around 39 C, Weathernews said.