Extreme Heat Watch

* WHAT...For the Extreme Heat Warning below 4000 feet, dangerously hot conditions expected below 4000 feet, with daytime temperatures ranging from 98 degrees at Havasupai Gardens, to 112 degrees at Phantom Ranch. For the Extreme Heat Watch below 4000 feet, dangerously hot conditions possible below 4000 feet, with daytime temperatures ranging from 99 degrees at Havasupai Gardens, to 113 degrees at Phantom Ranch.

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

* WHEN...For the Extreme Heat Warning, from 10 AM Monday to 8 PM MST Wednesday. For the Extreme Heat Watch, from Wednesday evening 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.