* WHAT...Temperatures of 92 to 98 degrees F expected. * WHERE...Central and Southern Willamette Valley, Northern and Central Coast Range Valleys and Mountains of Oregon, Foothills of the Northern and Central Oregon Cascades, Central Columbia River Gorge and the Hood River Valley, Willapa Hills and Adjacent River Valleys of Pacific and Wahkiakum Counties, Lower Columbia River and Cowlitz River Valleys, Outer Southeast Portland Metro, West Columbia River Gorge of Oregon above 500 ft, North Clark County Lowlands, and South Washington Cascade Foothills. * WHEN...From 11 AM Sunday to 11 PM PDT Tuesday. * IMPACTS...Hot temperatures may cause heat illnesses. * ADDITIONAL DETAILS...Peak heating days will be Sunday and Monday with a slight cool down on Tuesday. Overnight temperatures will remain elevated Sunday night into Monday morning, and Monday night into Tuesday morning. Night time temperatures ranging from 60 to 65 degrees F will lead to limited overnight relief.