With a nasty brew of heavy rain, cold, and headwinds forecast for Monday, authorities are scrambling to mitigate the misery of 23,000 runners in what could rank among the worst conditions in the history of the Boston Marathon.
More than 1,200 medical personnel will line the 26.2-mile course, waiting to treat runners for hypothermia or injuries. School buses will be converted to emergency shelters, and communities along the route are considering using public buildings as heated sanctuaries for shivering dropouts.
"It's extremely disappointing," race director Dave McGillivray said of the forecast, which called for heavy rain and easterly winds as high as 20 miles per hour.
As arriving runners looked to the skies yesterday, the Boston Athletic Association ratcheted up preparations for the 111th edition of the race, the world's oldest continuous marathon competition. The race has never been canceled because of weather, and Guy Morse, executive director of the BAA, said that only a major snowfall would stop this one.
"We'd only do if it there's a public safety issue." Morse said of a postponement or cancellation of the race, scheduled to start at 10 a.m. in Hopkinton.
The wheelchair race is also scheduled to proceed as scheduled, said BAA spokesman Jack Fleming.
Despite the dreary forecast, marathoners who picked up their numbers yesterday at the Hynes Convention Center seemed stoic about the weather, even excited about the extra challenge.
"If you've lived around here, you've trained in worse weather," said Tom Licciardello, 57, of North Andover, who will be running his 31st consecutive Boston Marathon. "If it's going to be bad, I hope it's really bad, because it will be an epic that you can tell your grandchildren, and it'll get bigger every year."
The National Weather Service predicted yesterday that the worst weather would hammer the region tomorrow night, with heavy rain and winds up to 30 miles per hour. The rain is expected to lighten by late Monday morning, but meteorologists said the storm might not moderate before noon, when the frontrunners are nearing the finish line at Copley Square.
In addition to potentially heavy rain and stiff winds, meteorologist Alan Dunham said marathoners could face temperatures no higher than the low 40s.
McGillivray said the conditions could slow the leaders by two or more minutes and back-of-the-packers by a half-hour.
Although the number of medical personnel will be the same as it has been for recent Boston Marathons, McGillivray said that a fleet of 500 buses, which are normally used to ferry runners and clothing bags back and forth from Hopkinton, will do double-duty this year as dry, heated shelters along the course.
The Red Cross also will be stationed at 25 locations along the route, as usual, and three tents for serious emergencies will be spaced along the hilly course. McGillivray said the BAA will try to provide heaters for many of those posts.
In addition, the Massachusetts Emergency Management Agency will have up to 100 staff members at its bunker in Framingham, said Peter Judge, the agency spokesman.
"There's no specific template for this," Judge said. "There's concern, obviously, but we feel comfortable about the safety of the runners, as long as they take precaution."
Deveda Mah, a psychologist and marathoner from Edmonton, Alberta , said she was crestfallen when she heard a rumor that the race could be canceled. Mah recently finished chemotherapy and radiation treatment for breast cancer, but she is a long-distance fanatic who has been looking forward to running her second Boston Marathon this year.
Mah said her doctors do not know she is running Monday. "I think I'm OK; I'm feeling better," said Mah, who flashed an ear-to-ear smile as she held her race number, 17398. "At least I have my hair back," she said of the effects of chemotherapy and radiation. "I'm so happy."
Mah said that she is not concerned about the weather, but that she will not take the elements lightly and will dress appropriately.
For marathoners, dressing appropriately will mean layers of noncotton clothing, staying hydrated, and paying strict attention to any symptoms of hypothermia.
If hypothermia develops, runners will discover that they "are going to be physically cold, and they'll be shivering," said Chris Troyanos, medical coordinator for the race. "When the shivering stops, that's an absolute sign that you need to seek medical attention. And by that time, it's very difficult to deal with."
In addition to layers, Troyanos recommended that runners wear a wool or stocking hat to retain some of the body heat that escapes through the head and gloves or mittens. He said he expects 5 to 8 percent of the runners to need treatment.
Dr. John Boyle, a runner and orthopedist from Beverly, advised runners with hypothermic symptoms to "get off the course and get into warm clothing." This will definitely be a problem if it's raining, because you lose body heat much quicker if you're wet."
Troyanos also urged runners "to take some responsibility as far as the decision-making process about whether this is the right thing for them."
Marathoners also need a good exit strategy, Troyanos said, in which they can meet their families and loved ones quickly after the race. Otherwise, standing after the finish in Copley Square, which traditionally is a windy and cold place, will be an invitation for hypothermia.
John Powers and Raja Mishra of the Globe staff and Globe correspondent Amanda Bergeron contributed to this report. Brian MacQuarrie can be reached at email@example.com.