HUD must be doing something to measure them as well, since they have a category for "unsheltered". No idea how accurate it is.Seattle has volunteers who literally beat the bushes to do an annual count of the homeless who are living on the streets in shelters, vehicles and tent
encampments or in the wooded areas. If you wanted to you could look up those statistics. It is a lot more accurate than the counts that just list the people using shelters and official social services.
Portland and Seattle and really the entire west coast is a homeless magnet... because they are accommodating, relatively... and the climate isn't too bad. I definitely wouldn't extrapolate their trends to the whole country.