TOKYO - Tokyo marks exactly two years to the start of the Olympic and Paralympic Games on Tuesday (July 24) amid a murderous heatwave that is taking its toll throughout Japan.

The mercury soared to a scorching 41.1 deg C in Kumagaya city in Saitama prefecture in the Greater Tokyo region at 2.16pm on Monday (July 23), setting a new record for the highest temperature that has ever been logged in all of Japan.

This topped the previous record of 41.0 deg C set in August 2013 in Kochi prefecture in western Japan.

In the Japanese capital, the temperature also breached 40 deg C for the first time on Monday (July 23), with a reading of 40.8 deg C registered in the western district of Ome.

At least 77 people, mostly the elderly, have died, including a pupil who fell unconscious after a school outing last week, and more than 30,000 have been taken to hospital for heat exhaustion or heat stroke this month.

The crippling heat has also complicated relief efforts in western Japan, which was pummelled two weeks ago by historic rainfall that caused flooding and landslides, killing at least 222 people and displacing thousands from their homes.

A tally by public broadcaster NHK on Monday (July 23) showed that as many as 38 Tokyo residents could have died due to the heatwave this month, with 21 deaths recorded between Friday and Sunday. The victims were in their 40s to 90s.

At least nine people died on Monday, the Kyodo news agency said. In the south-western prefecture of Miyazaki, nine high school students who were watching a baseball game were stricken and taken to hospital, with some in severe condition.

Two Singaporeans who live and work in Tokyo also experienced symptoms of heat exhaustion over the weekend.

Ms Nur Rosmawati, 27, who works in international business development at a publishing house, told The Straits Times that she "blacked out for a few seconds" during a five-minute walk between her home and a nearby convenience store on Saturday morning (July 21).

"It was not sheltered but I had my umbrella with me. At the entrance of the convenience store, I started to feel faint and my ears started to ring," she said, adding that she recovered after she ate an energy bar and had a hydrating drink.

"The humidity now is somewhat similar to that in Singapore, but the temperatures are way higher," she said.

What makes matters worse is that malls and offices in Tokyo tend not to turn down the air-conditioning, as part of energy conservation measures.

Ms Layla Tan, 28, an international business adviser who has lived in Tokyo for 3½ years, too fell victim to heat exhaustion on Sunday.

"First I felt a migraine-like headache. I drank lots of water but by then it was too late," she said. "The headache got worse, and I started feeling nauseous, followed by muscle aches."

She said she sought outpatient treatment when she felt better. The Tokyo Fire Department dispatched ambulances 3,125 times on Sunday alone, the largest number in a single day since it began emergency services in 1936, Kyodo reported.

While weather forecasts show some slight respite for Tokyo this week, Japan Meteorological Agency (JMA) official Motoaki Takekawa told reporters on Monday that wide areas across Japan will continue to experience temperatures above 35 deg C until early August.

This is due to two high-pressure systems that have compressed warm air to the ground, akin to two thick layers of blankets covering the Japanese archipelago, the JMA said.

The JMA has issued advisories covering nearly all of Japan except northernmost Hokkaido - which has been spared the heatwave - urging people to drink more water and take adequate measures against heatstroke.

Dr Joel Myers, president of weather forecasting site AccuWeather, said in a statement that the actual death toll from the heatwave may be well higher as heat-related deaths are difficult to pinpoint, particularly those complicated by deteriorating health issues.

"The elderly and those with pre-existing conditions, such as asthma and heart failure, are likely to face declining health due to exacerbation of their conditions due to weather," he said.

"Heat exhaustion and stroke, dehydration, migraines, loss of sleep and mood alteration can all occur due to dangerous heat."

In Australia, where summer temperatures can soar to as high as 45 deg C, the intense heat has killed more people than any other natural hazards.

The United States' Centers for Disease Control and Prevention also said that the elderly are more prone to heat stress than young people because they do not adjust as well to sudden changes in temperature.

The elderly are more likely to suffer from chronic medical conditions that alter the normal body response to heat, or are more likely to take prescription medicine that may inhibit perspiration.

AccuWeather noted that the current heatwave blanketing Japan has led to temperatures "well above" the normal high temperatures in July, which typically average 29 deg C in Tokyo.

Even so, Tokyo Governor Yuriko Koike told a news conference on Monday that she was not taking any chances when the Tokyo Olympics kick off in two years.

Describing the recent experience as akin to "living in a sauna every day", she vowed to ensure adequate measures will be taken to protect both athletes and spectators.

These include mobile misting stations and asphalt-insulating technology that is said to lower temperatures by as many as 8 deg C.

Beyond that, a host of events will begin earlier in the so-called "early-bird Olympics", with the men's 50km race walk to kick off at 6am instead of the originally-scheduled 7.30am.

"We will continue our efforts to push for new technology for all athletes, spectators and inbound visitors, so that our cumulative efforts will make it more comfortable for everyone," she said.