The National Weather Service said Saturday there was no rain the forecast for race day but highs could hit 97 with a heat index of around 100 degrees.
The sultry temperatures could take a toll on the thousands of spectators who will be in the stand at the Speedway Sunday, and drivers and pit crews face a potentially rugged day as well as potential on-track temps reaching a dizzying 140.
The race course was turned over to the Legends race Saturday following the final practice laps the previous day.
Dario Franchitti and Scott Dixon turned in the fastest times in Friday's workouts with speeds around 222.3 miles per hour. Franchitti said his Honda-powered Target Chip Ganassi Racing car experienced some slipperiness on the sun-baked course.