Kenyan runners took the top three spots in both the men's and women's races, with Levy Matebo and Bernard Kipyego finishing second and third, respectively for the men.
American Jason Hartman came in fourth with an official time of 2:14:31.
Last year's winner and race record holder Geoffrey Mutai dropped out just before the 19-mile mark of the 26.2-mile race because of cramping.
Sharon Cherop took the women's title with an official time of 2:31:50, edging out compatriot Jemima Jelagat Sumgong, who crossed the finish line with a time of 2:31:52.
Monday's forecast, with temperatures in the mid-80s, prompted race officials to issue warnings to the 27,000 registered participants ahead of the race.
Korir, 29, admitted to cramping up at about mile 13, but told WBZ-TV after the race, "I just kept praying and singing and asking God for the energy."
More than 4,000 runners opted to skip the historic event, while several others dropped out as temperatures soared, according to WBZ-TV.
The heat stalled the pace of this year's race, with Korir's winning time almost 10 minutes slower than Mutai's record set last year.