People across Oregon’s Willamette Valley and Southwest Washington are likely to face extreme heat early this week.According to the National Weather Service, there is at least a 70% chance that temperatures will exceed 90 degrees across the region after rebounding into the low-to-mid 80s on Sunday afternoon.The weather agency has issued a heat advisory from 11 a.m. Monday through 11 p.m. Tuesday for much of northwest Oregon and Southwest Washingt…