On your mark, get set, hydrate: With temps expected to reach the 80s Sunday, Chicago Marathon runners will need to be careful.

Scott Sexton, of Stevens Point, Wisconsin, has his medal and a bag of ice on his head at the finish of the 30th LaSalle Bank Chicago Marathon on Oct. 7, 2007, which was cut short because of the heat related stresses and injuries to runners. (Chuck Berman / Chicago Tribune)