At about 2:16:30 there is a shot of the fire moving towards the city, but the mismatch in the night sky as well as the fire not moving shows that it is just a matte painting.
The geographic landmarks used in the movie are all made up and are not in the Portland area at all.
Portland is a city that ranks 3rd in total yearly rainfall, but the premise of the story is that the city has had a 50 year drought meaning the backstory is built upon climate conditions in the past that never happened.