* WHAT...Dangerously hot conditions expected. Afternoon temperatures in the desert valleys will climb into the 108 to 114 degree range, and may exceed 115 along the Colorado River Valley and 120 in Death Valley. Overnight lows generally 80 to 95 degrees. * WHERE...Portions of northwest Arizona, southeast California, and southern Nevada including the Greater Mojave Desert region. * WHEN...From 10 AM PDT / MST Thursday to 8 PM PDT / MST Monday. * IMPACTS...Heat related illnesses increase significantly during extreme heat events.