For some Seattle residents, the sneezing and itchy eyes this fall rank among the worst allergy symptoms they can remember. The season has been unusually heavy even for transplants whose first autumn in the city was noticeably milder.

Pacific Northwest fall allergy seasons are typically driven less by pollen than by mold spores, which thrive in the region's wet leaf litter and damp ground cover this time of year. That mold exposure offers one explanation for the symptoms. There are also reports of yellow dust on cars and patios, attributed to specific pollinating trees -- evergreens and ornamental cedars among them. Those trees can release pollen later into the year than most people expect, well past what pollen-count trackers typically flag for November.

Allergies aren't the only explanation, though. This is also peak respiratory-illness season, with flu and cold viruses circulating widely enough that symptoms blamed on allergies could just as easily be an early virus. The uncertainty calls for similar precautions either way -- treat new sneezing and congestion like the start of a cold, mask up around others, and don't assume antihistamines alone will fix it if a flu or COVID test comes back positive.

It's a near-annual conversation in Seattle: newcomers arrive expecting hay fever season to end with summer, and instead find a second, soggier allergy season waiting in October and November -- assuming it's allergies they're dealing with in the first place.