The 2012 Boston Marathon is off and running, though there may not be quite as many participants as expected doing the actual running due to the potentially dangerous heat expected during Monday's race.
The temperature was 69 degrees when the wheelchair racers left Hopkinton for the start of the race at 9:17 a.m. ET, and had risen to 71 when the women started at 9:32 and was up to 73 when the rest of the field took off at 10.
By the time the runners get to Boston's Back Bay, they could be facing temperatures in the mid-80s.
The heat already appears to be taking its toll on the participants, with the leaders running at a slower than usual pace early on. The elite women ran the first three miles at a pace that would have them finish in around 2 hours, 38 minutes -- which would be the slowest Boston Marathon women's time since 1978.
It's a stark contrast from last year, when perfect temperatures helped Geoffrey Mutai run the fastest marathon ever (2 hours, 3 minutes, 2 seconds). He and fellow Kenyan Carolina Kilel, who won the women's race last year, are back to defend their titles.