Japan logged its highest-ever temperature of 41.1 C on Monday as a deadly heat wave continued to grip wide areas of the country, claiming more than 70 lives and sending tens of thousands of people to hospitals over the last two weeks.

The extreme heat left 77 people dead and sent more than 30,000 to hospitals across the nation from July 9 to 22, according to the Fire and Disaster Management Agency and a Kyodo News tally.

(Children in Tajimi, Gifu Prefecture)

The extraordinary heat prompted the Japan Meteorological Agency to hold an unusual news conference, saying, "This heat is a threat to life. We recognize it as a natural disaster."

The agency warned the public to take preventive measures against heatstroke, as scorching temperatures are expected to continue for two more weeks.

The mercury hit the record high in Kumagaya, Saitama Prefecture, near Tokyo at 2:16 p.m., eclipsing the previous record of 41.0 C marked in August 2013 in Shimanto, Kochi Prefecture, in western Japan, while Tokyo also logged its all-time high of 40.8 C in the city of Ome, according to the agency.

"I've been hearing lots of ambulance sirens recently," said Hayato Nakamura, a 12-year-old junior high school student, who was playing in a water fountain with his friends in a park in Kumagaya. "The water is lukewarm and it dries up so fast."

Kazumi Kaneko, a 66-year-old resident of the city, said she keeps her home air conditioned for 24 hours to avoid heatstroke.

Temperatures in Tajimi, Gifu Prefecture, rose to 40.5 C after the central Japan city already reported 40.7 C last Wednesday, the agency said.

Of the agency's 927 observation points across the country, nearly 70 percent, or 627, recorded temperatures over 30 C, and 241 registered readings surpassing 35 C.

Risk of heatstroke rises when the temperature is over 40 C, as even wind would be so hot it could heat up the body rather than cooling it down, according to Seichi Horie, a professor at the University of Occupational and Environmental Health in Kitakyushu, Fukuoka Prefecture.

(Kumagaya, Saitama Prefecture)

The heat wave has persisted for two weeks right after torrential rains caused massive flooding and landslides in the country's west.

On Monday, at least 13 people died in nine prefectures of Saitama, Ibaraki, Gunma, Toyama, Aichi, Osaka, Hyogo, Kumamoto and Mie, and 2,377 people were taken to hospitals, according to another Kyodo News tally.

Among the fatalities was a 91-year-old woman who was found collapsed in a field in Ibaraki Prefecture and was later pronounced dead at a hospital.

In Saitama Prefecture, at least two elderly women died, including an 85-year-old who had told acquaintances she rarely used air conditioning, and a 72-year-old who was found collapsed in a room without the air conditioner on.

Nine high school students watching their school baseball team play in the southwestern prefecture of Miyazaki were taken to hospital, with some in severe condition.

The Tokyo Fire Department dispatched ambulances 3,125 times in the capital on Sunday alone, the largest figure for a day since it began emergency services in 1936, apparently due to a surge in the number of people falling ill from the intense heat.

As of Monday, the number of people who have been taken to hospitals by Tokyo's ambulances due to heat exhaustion or heatstroke this year stood at 3,544, already surpassing the 3,454 for the whole of last year, according to the department's preliminary report.

More on the heat wave in Japan:

At least 11 dead Sat. as heat wave continues to grip Japan

Olympics: Tokyo 2020 marathon to be held early morning to avoid heat