Further research tells me that it’s alder pollen in particular that is rampant at the moment. Alder trees are apparently abundant in the Pacific Northwest, which maybe explains why I did not grow up with this problem in the spring. I looked outside our apartment but I can’t tell which tree is which because none of them have leaves yet, but I would not be surprised if some of them are alder. I looked through my blog from last year around this time and found nothing, but thinking back there weren’t any trees close to our windows at our old house since our entire yard was paved over, Vancouver style.
Of possible interest: