Portland does not have ice storms every year.
Not every year, true, but I recall pretty good ice storms every few years in the 60s, 70s, and early 80s before I moved out of Oregon in 1985. First you'd have several days of very cold dry air coming down from east of the Cascades and pouring down the Columbia Gorge, freezing the ground god and hard. Then a warmer and wetter mass of air would come off the Pacific, ride up over the cold air, and drop rain. There would be a coating of perfectly clear ice on everything, as much as a half inch thick.
The weight of the ice would bring down tree limbs and wires all over the place. Driving in the hills was really difficult, even with chains. One of my brothers had a pair of hockey skates and he'd go skating on the streets around the neighborhood.
I don't know if ice storms in Portland are less common now, but they weren't rare back then.