Volcano evacuation route sign. Hazards of Mount Rainier. Mount Rainier, the highest (14,410 feet / 4392 m) volcano in the Cascade Range, towers over a population of more than 3.3 million in the Seattle Tacoma metropolitan area, and its drainage system via the Columbia River potentially impacts another 500,000 residents of southwestern Washington and northwestern Oregon. Mount Rainier is the most hazardous volcano in the Cascades not only in terms of its potential for eruption, but also the risk of producing major debris flows even without eruption.