It all depends on acclimation. If a runner has been training at altitude with runs in the morning at 50 deg F, then they will be in big trouble at this race. If they have moved their training to a hot and humid coastal area, they will be able to get through it. My son plays soccer on a club team. They had practice and games in the afternoon when it was 100 deg+. No one had any problem with the heat because the kids had been out playing in the heat all summer, whether at camp or just messing around outside at home. Before Osaka and Daegu, a lot of distance runners spent time in Houston, TX or Florida to acclimate. That is the key.
Of course, the times will be crap. Women will not break 2:30 and men will be over 2:10. I would not at all be surprised to see winning times in the 2:15 range for men and 2:35 for women, maybe even slower.