My concern with Portland is that it can be washed away by a massive tsunami any day now. Reference: https://www.newyorker.com/magazine/2015/07/20/the-really-big...
Portland is ~80 miles inland from the pacific ocean - and the odds of a tsunami coming up the columbia river from the pacific, and still having much destructive power to do more than just flood, is again, basically nil - it would literally need to be a perfect storm for it to work.
So even the biggest tsunami the world has witnessed wouldn't come close.
I'm not sure there's such a thing as a city that's not vulnerable to at least one climate change or natural disaster threat.
Denver seems pretty safe. No earthquakes, safe from rising seas, no hurricanes or tsunamis.