Peres Jepchirchir, 27, of Kenya won the women’s Olympic marathon in 2 hours 27 minutes 20 seconds on Saturday in Sapporo, Japan, 500 miles north of Tokyo, where officials moved the 26.2 mile race in a preventive but futile attempt to escape the heat and humidity that have smothered the Summer Games.

Brigid Kosgei, 27, of Kenya, the world-record holder, took silver in 2:27:36. And Molly Seidel, 27, of the United States, running only her third marathon, won a surprise bronze in 2:27:46, staying among the leaders from the start. She became the third American woman to win a medal in the Olympic marathon. Joan Benoit Samuelson won the inaugural race at the 1984 Los Angeles Games, and Deena Kastor took bronze at the 2004 Athens Games.

Hours before the start, the race was moved up an hour to 6 a.m. to slightly moderate the effects of a record heat wave on Hokkaido, the northern Japanese island where Sapporo is. But it was swampy at 78 degrees Fahrenheit, with 82 percent humidity, as the race began. Many runners wore hats and sunglasses and tried to find narrow areas of shade at a cautious pace. At least 15 of the 88 entrants would drop out.

Sapporo, which hosted the 1972 Winter Olympics and is a candidate for the 2030 Winter Games, was chosen as the marathon site two years ago. It is one of the world’s snowiest cities, averaging 191 inches of snow per year. But that was no consolation on Saturday. The city can get uncomfortably warm in the summer. The winning time was the second slowest in the 10 women’s Olympic marathons, but time did not matter on this boggy morning.

Winning mattered. Surviving mattered.

As every weekend jogger knows, it becomes difficult for distance runners to dissipate body heat in hot, humid conditions. Ice baths for the Olympic runners were set up in first aid and recovery areas inside Odori Park in Sapporo, where the marathon began and ended, according to the Asahi Shimbun newspaper. Fourteen water supply tables were set up along the course, nine of them supplied with bags of crushed ice. Ambulances were to follow the runners during the race, the newspaper reported.

The last time Tokyo hosted the Summer Olympics, in 1964, the Games were held in October. But that is a time of year now devoted by television networks to endless American football and international soccer. An Olympic marathon staged in August in these conditions can take a heavy toll.

In the first couple of miles on Saturday, Meryem Erdogan of Turkey limped along then sat on the ground, grabbing her legs. She became the race’s first casualty. Lonah Chemtai Salpeter of Israel placed an icy towel or a bag of ice under her blue hat at a water stop around four miles into the race. Others draped towels around their shoulders. Just before seven miles, Seidel, wearing sunglasses and kinesiology tape over her left knee, stuck a small bag of ice beneath her singlet. Eunice Chebichii Chumba of Bahrain placed a bag of ice on her head.

By nine miles, the field had dispersed, the lead pack winnowed to 18 runners. At 10 and a half miles, Zeineba Yimer of Ethiopia, considered to be a contender, walked along the side of the road. The lead pack, now splintered to 11 runners, reached the halfway point in 1:15:14.

At 30 kilometers, or 18.6 miles, Seidel ran at the front of nine runners as the course was dappled in shade. The temperature on the tarmac was above 100 degrees, according to the NBC telecast. Even some of the greatest runners who have faced the worst heat began to falter. Ruth Chepngetich of Kenya, who won the 2019 world marathon championship in brutal conditions in Doha, Qatar, where the temperature was still 90 degrees at midnight, fell away and began walking.

At 20 miles, the pack was down to seven contenders, then five, then four who would decide the three medals. NBC showed a note that Seidel had written in the fourth grade: “I wish I will make it into the Olympics and win a gold medal.”

At 23 miles, Jepchirchir and Kosgei began to pull away. Another contender, Chemtai Salpeter of Israel, trying to win the country’s first-ever medal in track and field, could not continue. Seidel had the bronze if she could hold on.

With about a mile and a half remaining, Jepchirchir, the world-record holder in the half marathon for a women’s-only race with a 1:05:16, began to draw away from Kosgei. Kosgei, whose world record of 2:14:04 was set at the 2019 Chicago Marathon, began to flail.

Earlier in the race, Jepchirchir had run for miles with a bottle of fluids tucked into her shirt to keep a store of carbohydrates available. As she approached the finish, what seemed to be a small bag of ice stuck out of her singlet. At the tape, she smiled, then bent over and seemed to pray.

It was the second consecutive Olympic marathon victory for a Kenyan woman. But Jemima Sumgong, the 2016 winner, is now serving an eight-year ban for doping. Jepchirchir’s victory is being seen as a matter of redemption and a hoped-for indication of restored integrity.

Seidel began to pump her fists, point to the “U.S.A.” on her jersey, and scream as she neared the finish. Until the 2020 Olympic trials, she had never run a marathon. Saturday was only her third. But she had run smartly, confidently and patiently in awful conditions. And she was now an Olympic medalist.