Extreme Heat Watch

* WHAT...Dangerously hot conditions possible below 4000 feet, with daytime temperatures ranging from 100 degrees at Havasupai Gardens, to 113 degrees at Phantom Ranch.

* WHERE...Lower elevations of the Grand Canyon.

* WHEN...From Tuesday morning through Saturday evening.

* IMPACTS...Most individuals will be at risk for heat-related illnesses without effective cooling or adequate hydration, especially with prolonged outdoor exposure.