* WHAT...Dangerously hot conditions below 4000 feet, with daytime temperatures ranging from 101 to 104 degrees at Havasupai Gardens and 111 to 114 degrees at Phantom Ranch.
* WHERE...Lower elevations of the Grand Canyon.
* WHEN...Until 8 PM MST Saturday.
* IMPACTS...Most individuals will be at risk for heat-related illnesses without effective cooling or adequate hydration, especially with prolonged outdoor exposure.