Cedars. I don't know if Deodar cedar sheds in fall, but Atlas cedars do!

Thanks. Conditions this year must have been just right for the pollen to accumulate over a wide area.

Here is a chart re: pollen for Seattle. I would think it's similar in Portland. However, it seems to feature native species, so perhaps there are ornamentals with different timetables. I would have guessed the pollen you're seeing is from grass. It's been so dry that perhaps the season has been extended. With all the ornamental grasses being used in landscapes these days, it's miserable for those of us with grass allergies when they release their pollen. https://www.nwasthma.com/pollen-count/