I am also running a fall marathon (Detroit, Oct 15) and will likely have a rest period and ramp up similar to what @DopeyBadger said. Right now I'm questioning my sanity training for a marathon in the summer heat! At 5:00am this morning it was 73 degrees with Florida-like humidity - I was dying during my easy 3 mile run!
I feel your pain. We are on day 3 of a heatwave here in New Jersey and it is supposed to break tomorrow. My "easy " run this morning was quite ugly! Hope it cools down a bit for you.