Boston Athletic Association officials told The Boston Globe they were amazed only 328 runners took them up on a pledge of a place in next year's marathon if they did not feel up to running with temperatures in the high 80s. A total of 21,603 runners finished the course Monday, about 96 percent of those who set off.
More than 10 percent of the runners were treated at medical aid stations along the way. A few people ended up in hospitals and at least nine were still in critical condition Tuesday, although officials say all are expected to survive.
"Everybody knew what was coming and everybody was prepared for it," said Tom Grilk, the BAA executive director. "It certainly wasn't a day that we wanted, but it was a day that we had planned for."
The marathon, run on Patriot's Day to honor Paul Revere's Ride, is known for extreme weather. Between 1905 and 1909, conditions ranged from temperatures breaking 100 to sleet; in 1939 there was a northeast storm and in 1976 a race immortalized as the Run for the Hoses when a combination of high temperatures and poor planning had runners scrambling for water.
In 2004, the number of heat casualties set a record. Chris Troyanos, the medical services coordinator, said that experience taught him to think of the marathon as a "planned mass casualty event."