I know less about Portland, but both Seattle and Vancouver have extremely good local economies and expensive housing and housing shortages.

It's likely that there's a relationship here between people moving to these cities for better economic opportunities, then combinations of misfortune, rising rents and housing scarcity resulting in people becoming at risk of homelessness or being on the street.

Vancouver has the best winter in Canada -- you don't have to deal with -30C winter

Hey, maybe they'll be gone by spring.