Nearly 22,500 participants braved unseasonably balmy conditions at the 116th running of the storied 26.2 mile race. Organizers stocked extra water and pleaded with runners to slow their pace to avoid heat stroke. Some 4,300 participants registered to run opted to sit out.
"It was brutal, just brutally hot," said 38-year-old runner Jason Warick of Saskatoon, Saskatchewan, who took an ice bath before the race to cool his body. "Around 15 miles the wheels just came off. Then it was just about getting home."
Organizers said that as of the late afternoon, more than 800 runners had received some level of medical attention, and 50 were taken to hospitals in ambulances. One person was taken from the course in serious condition in Wellesley, though the details of their condition were unavailable Monday.
Medical volunteers scanned the finish line for runners displaying signs of heat stroke, assisting those in need to nearby medical tents. By mid-afternoon, dozens of wheelchairs carrying pale and weakened runners stretched outside the tents.
"I've never seen anything like (that)," said 35-year-old Desiree Ficker of Austin, Texas, who used salt supplements during the race to stay moving. "It was really hard seeing the confusion on people's faces."
Organizers said careful preparation and responsible runners prevented more serious problems on what was one of the hottest marathons in Boston history.
Heat was also a problem in the 2004 marathon, when 2,041 of the 18,002 participants who started the race sought medical attention. That's a higher percentage than any year in memory, according to organizers.
"This was the day we were preparing for," said Thomas Grilk, executive director of the Boston Athletic Association. "The god of marathoning, she smiled on us."
Temperatures prompted 30 additional physicians to volunteer at the last minute. Race organizers and volunteers pleaded with runners to put their safety ahead of their competitive drive.
"Today is not the day to run a personal best," said Garth Savidge, rehab supervisor at Newton-Wellesley Hospital, who was helping runners before the race. "Everybody is being a little extra cautious."
Organizers said the highest temperature recorded Monday during the marathon was 89 degrees in Framingham at 12:30 p.m.
Registered runners who decided not to run because of the heat will be given an opportunity to run in next year's race. Susie Eisenberg-Argo said she never considered skipping her ninth consecutive Boston Marathon. The 50-year-old Sugarland, Texas resident said before the marathon that she would force herself to slow down instead -- and make sure she stopped for water along the way.
"It's a challenge to back off and say, `I'm just going to take it a little more slowly,"' she said. "Most of the people here know what they're doing."
Matt Manning finished the race in 2 hours and 34 minutes -- a full 10 minutes slower than his pace last year. He said the heat set in after the first several miles.
"It was direct sun the whole way," said the 32-year-old Baton Rouge, La., man. "I was hanging around through 10K or so, then I started to slow down.... I may move to Alaska or something to get away from the heat."
The famously welcoming crowds that line up to watch the marathon did their best to help out the athletes, cheering them on even as they themselves sweated through an unseasonably warm April day.
June Ramlett, 83, has been watching the marathon since she was a little girl. The Hopkinton, Mass. woman made sure to have a good vantage point for the starting line. She drank from a plastic jug of water to stay cool.
"It's really something to see," Ramlett said as thousands of runners hit their stride. "I've watching it for years and it's still very special."