Fact: All the top-10+ marathons of all-time have been run at temps in the 40's F... even 50+ has been shown to be slower. This is a typical temp at Rotterdam and usually London. By the time the leaders were finishing Chicago, temps were already in the 70's... The race director tried to make it sound like it was no big deal before the race, but the stats say no one had a shot at a record today.
Not to mention many runners were stuck to their time goals, and if you're not capable of running your goal in the heat but try to anyways, you are doomed to crash.
70+ degrees may have a small effect over an 800m, but it is extremely taxing over 42,195m. People seem disappoined with some of the top American's times, but looking at their splits and taking the heat into account (and the fact that they were stuck on starting out in 1:05) it's about what I would expect. Very impressive for Jason Hartman, too... his run may be about as good as anything his HS teammate Ritz has ever done.