An Excessive Heat Warning will be in effect for parts of Northern Arizona starting Friday and lasting through the Labor Day Weekend. The warning will be in effect from Friday morning through Monday evening for areas below four-thousand feet. The warning includes Cottonwood, Camp Verde, and other lower elevations of Yavapai County, along with the lower elevations of the Grand Canyon. Forecasters say extreme heat will significantly increase the potential for heat related illnesses, particularly for those working or participating in outdoor activities. If you are going to be outdoors this weekend, drink plenty of fluids, stay out of the sun and in an air-conditioned room when you can and check up on relatives and neighbors. Young children and pets should never be left unattended in vehicles under any circumstances. This is especially true during hot days.