I think having trained in Georgia is going to pay off on Sunday. The high for Sunday is in the mid-70s. That's about 15-20 degrees warmer than most marathoners would prefer. A month ago, I could see my breath during my trip to Chicago and was worried it would be too cold, but that doesn't look to be the case for this weekend.
Luckily, it won't be as hot as it was last year when they had to cancel the race. Last year the temperature pushed 90 degrees. Race officials have put the event warning system at "yellow/moderate", but it wouldn't surprise me if they raised it before Sunday. As long as it doesn't go to black, they'll still let people run.
Regardless, there's lots of SPF 50 sunblock in my future on Sunday and I'll definitely need to wear my hat. I've added a weather gadget to the right so you can see the forecast.