* WHAT...Dangerously hot conditions possible. Afternoon temperatures 102 to 106. Major Heat Risk. * WHERE...In Arizona, Gila River Valley and Parker Valley. In California, Chuckwalla Valley and Palo Verde Valley. * WHEN...From 10 AM MST /10 AM PDT/ to 8 PM MST /8 PM PDT/ Thursday. * IMPACTS...Heat related illnesses increase significantly during extreme heat events. Overexposure can cause heat cramps and heat exhaustion to develop and, without intervention, can lead to heat stroke.