The problem with people saying that everyone has the same conditions and it is a race so it doesn't matter is that:
Not everyone is affected by the heat equally. This race becomes about who can take the heat the best
The taller you are the worse you do in the heat because you have less surface area / volume ratio
C'est vrai. In 2004 I went to Boston from Houston. As a small female, having trained in Houston, I did not run my best time, but got my highest placing of the 7 Boston Marathons I've run. I passed MANY of my unfortunate larger male runner friends, all of whom are better runners than me. The finish line was gross -- folks throwing up and collapsing all over the place.
It's looking like small females from the south may have a decent run Monday. Good luck to all, and run within your limits, so you may live to run another marathon with ideal weather!
I thought the finish line in 2004 was excellent. I have fond memories. Finished in around 3 hours in 300-somethingth place, none of my friends were finished yet so I went to the medical tent where 3 very cute Danish med students were attending to my every need. Well, ALMOST every need. Totally refreshed 20 minutes later I went out to enjoy the awesome weather and watch the mayhem. The news said 1100 runners had received medical attention. I guess I was one of them.
Timewise I think the heat cost me 8-10 minutes but I had already stopped worrying about that by about Newton.