The Tokyo Olympics organizers, already struggling to contain the spread of Covid-19, are contending with another obstacle largely beyond their control: a heat wave.
Day after day of 90-plus-degree heat and high humidity has forced organizers to reschedule rugby matches and mountain biking competitions and move some track and field events to early morning hours or dusk to avoid the roasting afternoon sun.
Other events, like the marathon and race walking, have been moved completely out of Tokyo to the cooler city of Sapporo, capital of the mountainous northern Japanese island of Hokkaido and the site of the 1972 Winter Olympics.
For the athletes competing in Tokyo, the organizers have erected cooling tents, hauled in water-mist fans and started providing ice cream to the army of volunteers helping run the Games.
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At the beach volleyball arena at Shiokaze Park in Tokyo, organizers have started hosing down the sand after competitors complained it was burning their feet.
Russian archer Svetlana Gomboeva collapsed in the 91-degree heat Friday during a qualifying round, succumbing to the steamy heat that has been blanketing Tokyo for days and shows little sign of abating.
“It turns out that she couldn’t stand a whole day out in the heat,” coach Stanislav Popov told reporters at the archery range while Gomboeva’s teammates placed bags of ice on her head to cool her down.
Gomboeva was expected to recover, he said, adding that it was "the first time I remember this happening. In Vladivostok, where we were training before this, the weather was similar. But humidity played a role here."
The heat "definitely can take its toll on all of us, even the fittest people in the world," NBC News senior medical correspondent Dr. John Torres said.
Sweltering summers are nothing new in Tokyo. But thanks to climate change, the Tokyo Games are forecast to be the hottest on record, NBC News meteorologist Kathryn Prociv said.
Compared to 1964, which was the last time Japan hosted the Summer Olympics, the July and August temperatures in Tokyo are 2.7 degrees warmer, and there are now, on average, eight more days of 95-plus-degree weather than there were 57 years ago, Prociv said.
Recognizing the danger this weather could pose to the athletes, the International Olympic Committee and the Tokyo Games organizers released a series of recommendations created in partnership with the committee's medical division designed specifically to help prevent Olympians from overheating.
Torres said the intense focus of the athletes is one reason some are susceptible to heatstroke or dehydration.
“We adapt to the heat and humidity through what’s called thermoregulation, our body's ability to cool itself off,” Torres said. “For these athletes, they will have strong thermoregulation systems, but during their event, when they are pushing themselves to the limit of their abilities, their body doesn’t have the reserves it normally does to cool them off.”
“Because of that,” Torres said, “they can overheat very quickly, and since they are so focused on the performance, might not even notice it until it becomes dangerous and possibly life-threatening.”
High heat has figured in the deaths of at least two athletes competing in the Olympics, said David Wallechinsky, one of the founding members of the International Society of Olympic Historians.
“In the 1912 marathon, Francisco Lázaro of Portugal collapsed from overheating and died the following morning,” Wallechinsky said in an email to NBC News, adding that 23,000 people attended a memorial service for him in the Olympic Stadium in the host city of Stockholm in Sweden, where heat waves are rare.
In 1960, Danish cyclist Knud Enemark Jensen collapsed from heatstroke during the team time trial at the Summer Olympics in Rome. Jensen “cracked his skull and died in hospital,” Wallechinsky said. “He had probably taken amphetamines, but it was 108 degrees Fahrenheit that day.”
The death of Jensen, who was just 23, led the International Olympic Committee to institute drug testing of athletes at subsequent Olympic Games. Jensen’s defenders, however, insist an initial autopsy found no evidence of drugs and concluded he died of heatstroke.
The Tokyo Games are taking place during a state of emergency aimed at preventing the spread of Covid-19, and no fans are allowed in the stands although a number of athletes have already tested positive for the disease.
However, it means there is unlikely to be a repeat of the 1996 Atlanta Olympic Games when hundreds of spectators were treated for heatstroke.
Asked if he had any advice for the athletes who have to brave the burning heat, Torres said, “Keeping ahead of the inevitable dehydration is important since it’s very difficult to catch back up once your fluid is depleted. Also, understand and listen to your body.”
“If you start to feel lightheaded, nauseated or confused, stop and seek medical care,” he added. “Heatstroke can often go unnoticed until an athlete is in the danger zone, and that can be life-threatening.”