I can't run in the heat either - I melt. I did an OLY yesterday and it was 90 deg when I started on the run, was already warm from the bike and felt like I was in slow motion on the run (my time proved it too )

I'm not sure if its possible to acclimate to the heat or not, I think if its consistant perhaps you get used to it, but with decreased performance still.

Think its impossible in the NE as its never consistant, we can get 3 days in the 90's then it will be 60 deg :-)