Dangerously high temperatures in Japan have sent more than 10,000 people to hospitals for heatstroke in a single week, more than double the same period last year.

Some 10,857 people were transported by ambulance from July 13 through July 19, according to data released by the Fire and Disaster Management Agency on Wednesday. It was the first weekly total above 10,000 since this year’s monitoring period began May 1 and was about 2.4 times the 4,580 cases recorded the previous week.

The figure was also more than double the 4,958 people transported during the corresponding period in 2025.

Fourteen people died, while 321 were classified as being in serious condition and expected to require at least three weeks of hospitalization. About 37% of patients were moderately ill, while nearly 59% had mild symptoms.

People age 65 or older accounted for 6,734 cases, or 62% of the total. Homes were the most common location for heatstroke, accounting for 4,523 cases, followed by roads, with 2,326 cases, and outdoor public spaces, with 1,095.

Osaka recorded the largest number of transports among Japan’s 47 prefectures, with 1,041, followed by Aichi, with 797, and Tokyo, with 783. Tokyo’s total was more than double the 379 cases recorded during the equivalent week last year.

According to the Tokyo Fire Department, 453 people were transported to hospitals due to heatstroke on Wednesday alone.

The heat showed little sign of easing Thursday. Heatstroke alerts were issued for 39 prefectures from the Kanto region through Okinawa, according to the environment ministry and the Japan Meteorological Agency.

Temperatures were forecast to reach 40 degrees Celsius in Nagoya, Gifu and Kyoto prefectures and the Kofu region. Temperatures exceeding 40 C in Gifu and Kyoto would mark the first such readings in recorded history.

Some areas were expected to remain above 30 C overnight, increasing the risk of heatstroke even after sunset and impacting sleep.

Authorities urged people to remain in air-conditioned spaces, avoid unnecessary outings and drink water before feeling thirsty. Older people and young children require particular attention because they are more vulnerable to heat-related illnesses.

Heat stress is also rising worldwide as human-induced climate change makes heat waves more frequent and severe. Japan experienced record-breaking summer heat for a third consecutive year in 2025.

Heat waves and wildfires are also sweeping across parts of Europe. A fire in Spain’s Guadalajara province has burned about 32,000 hectares, while more than 100,000 hectares have been scorched nationwide this year. France has lost about 44,000 hectares to fires in 2026, and blazes have also affected Italy, Greece and Cyprus as temperatures across parts of southern Europe surpassed 40 C.