* WHAT...Dangerously hot conditions with high temperatures 103 to 108 possible. Low temperatures in the low to mid-70s, locally near 80 degrees in the Lucerne Valley. * WHERE...Apple and Lucerne Valleys. * WHEN...From Wednesday morning through Monday evening. * IMPACTS...Heat related illnesses increase significantly during extreme heat events. * ADDITIONAL DETAILS...Areas of major HeatRisk. Elevated low temperatures will limit overnight relief from the heat. Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors.