According to CBS, the heat was already slowing the pace of runners on the 26.2-mile race and creating potentially dangerous conditions for the rest of the 27,000 registered participants.
Afternoon temps are predicted to hit the mid-to-upper 80s, much higher than the average temperature for this time of year which is around the mid-50s, the Washington Post reported.
Officials are warning runners to take precautions.
Boston Athletic Association co-medical director Pierre d’Hemecourt said “Please don’t run the marathon” to runners with underlying medical issues, such as a cold or a virus that might leave them dehydrated, the Associated Press reported.
Organizers also said those who have either not run in the heat or a full marathon previously should wait till next year. The BAA is offering a deferment to those who want to sit it out, just as they did two years ago when a volcano erupted in Iceland making it impossible for hundreds of runners to reach Boston from Europe.
“Only the fittest runners should consider running," B.A.A. executive director Tom Grilk said "The risks... are simply greater than normal.”
“We’re asking runners who haven’t run previously to think about tomorrow and maybe coming back next year,” Boston Mayor Tom Menino said Sunday at the traditional pre-race pasta dinner, according to the Associated Press. “We don’t want have any accidents out there, or anybody overtaken by the heat.”