Approximately 45,000 runners from all 50 states and more than 100 countries were expected to take part in the 26.2-mile course. For the second year in a row, the forecast for weather was very warm. Ideal running conditions are actually in the 50s, but temperatures Sunday could reach the low 80s.
So, race organizers have been planning appropriately. They said they are adding more water stations and medical personnel to the course.
"You gotta take a personal check," marathon director Carey Pinkowski said. "You've obviously got to listen to your body. Tomorrow will be a great day. It may not be the day to break a record. So you want to be a little conservative."
With long running distances, one of the bigger issues is over hydrating. So, it is going to be a balance that the athletes will have to maintain, as well as a being realistic and recognizing that Sunday, they're not likely to break any personal records.
"You just have to drink a lot of water along the race and stay focused. As long as you stop every time they have water, you will be fine," said runner Shannon Bridges.
Those participating in Sunday's marathon are reminded that not stopping at a water station is not likely to mean a better finish time. Experts advise all runners to stop for fluids as necessary and to listen to their bodies.
"I don't normally take in a lot of fluids when I run, but I'm going to have to tomorrow," runner Lanni Marchant said. " Gonna play around and see what happens."
Crews were putting the finishing touches on the setup Saturday afternoon as athletes enter the stretch run of their preparation.
"I prepared, ran all summer in the heat, in the humidity. Been going to the sauna," runner Debra Sykes said. I'm ready for this."
At the Hilton on South Michigan Saturday night, the traditional marathon-eve pasta buffet was extended a couple hours to accommodate Jewish runners whose Yom Kippur fast ended at night fall. There were three kinds of pasta, salad and plenty of dessert.
University of Illinois wheel chair track coach Adam Bleakney is here from Champaign with his team of 17 athletes
"This is a great event for us," Bleakney said. " It's a fairly local event where we get in front of a ton of alum up here."
For those who are not running but will be coming out to watch along the route, parking bans will be in effect by 1 a.m. Sunday, and streets will close from 7 a.m. to 3 p.m., or until the last runner finishes.
Saturday night in Pilsen, signs were posted warning of the restrictions, and for several days, the city has left flyers on people's cars.