Excessive Heat Warning for Coconino County: 7/27 at 8am - 7/28 at 11pm. More Information. Excessive Heat Warning for Mohave County: 7/27 at 8am - 7/28 at 11pm. More Information. Excessive Heat Warning for La Paz County: 7/27 at 8am - 7/28 at 11pm. More Information. Learn more about how to stay safe in extreme heat and stay informed about future heat alerts.