A decision on canceling the 26-mile, 285-yard race would be made by public-safety officials and its organizer, the Boston Athletic Association, said spokesman Peter Judge of the Massachusetts Emergency Management Agency.

Current forecasts call for temperatures in the low 30s Fahrenheit (around zero degrees Celsius) with heavy rain and steady winds of 25-30 miles per hour (40-48 kilometers per hour), gusting to 50 mph.

"There's no threshold, but obviously conditions that are very unsafe for the participants or the community" would force the race to be called off, Judge said in a telephone interview. "We don't have a template."

Over the past 10 years, temperatures at the start in Hopkinton, Massachusetts, have ranged from 47 degrees in 1997 and 1998 to 83 degrees in 2004.

Judge said the race, which has 23,800 registered participants, would be canceled if it can't be run, rather than postponed. Jack Fleming, a spokesman for the organizers, said that decision was up to public-safety officials.

"Our plan right now is Monday," Fleming said.

Preparations

More than 100 people from the athletic association and emergency-management agencies held a regularly scheduled meeting today to discuss preparations for the race, which runs through seven suburban towns before ending in the city of Boston. The race traditionally takes place on Patriots Day, a Massachusetts state holiday that falls on the third Monday of April.

Judge said special preparations include the placement of pumps along the course where flooding is possible, installation of heat in the medical tents and parking of buses along the route to give people shelter from the elements.

"We're breaking new ground in dealing with this type of event," Judge said.