The organizers of Humana Rock ‘n’ Roll Marathon series in Chicago have canceled one of its three weekend races due to concerns over “excessive heat.”

Organizers canceled Saturday’s 5K race, set to begin at 7:30 a.m. in Grant Park, after temperatures were expected to be too dangerous for participants, race organizers posted to Facebook on Friday evening.

Temperatures are expected to reach 94 degrees on Saturday, according to the National Weather Service. The heat index is forecast to be 105 to 110 degrees.

The excessive heat warning is expected to expire by Sunday morning, when the Rock ‘n’ Roll will kick off its two other planned races, including a 10K and half marathon. Those races are still scheduled to happen.