The temperature is rising as the Chicago Marathon wears on and organizers are warning runners to be aware of the changing conditions.

Organizers have raised the alert level from yellow to red in their multicolored warning-flag system. Red warns runners it's potentially dangerous and conditions for running a marathon are not ideal.

Race spokesman Marianne Caponi said the temperature at noon Sunday -- four hours -- after the race started was about 85 degrees. When the race started it was 64 degrees.

Last year's marathon had to be canceled about four hours into the race because of scorching heat.

Caponi said red warning flags tells runners to consider adjusting their pace, pay attention to their hydration and be aware of how their bodies are reacting to the rising temperatures.