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Signs of spring: Weather tools give insight on tree pollen and bird migration

An early springtime view of Port Townsend Bay , as seen from the Larry Scott memorial trail on March 1, 2020.
Bellamy Pailthorp
An early springtime view of Port Townsend Bay, as seen from the Larry Scott memorial trail on March 1, 2020.

Do you doubt that spring has arrived in the Pacific Northwest? With cool temperatures and copious rain dousing much of the region lately, it can be hard to believe.

Just a couple of weeks ago, KNKX weather expert Cliff Mass talked about the typical arrival of "meteorological spring," when big storms cease and other weather changes indicate that for all practical purposes, winter has ended. It happens here a full month prior to the end of winter on the East Coast.


This week, Mass takes a look at tree pollen levels, which he says started spiking even earlier than the arrival of spring in the Northwest.

“Pollen season started about a month ago,” he says, based on air quality measurements in the region, which chart the amount of pollen in the air from species such as cedars and alders. “And those with allergies certainly have noticed it.”

What Mass found fascinating is the recent correlation between rainy days and times when the pollen count falls.

“The correlation was almost perfect. On days when we had rain, the pollen levels would plummet. On the other hand — dry periods — that would allow the pollen levels to go up,” Mass says.


Another sign of spring that weather hawks can see from their computer screens: seasonal bird migration, on the radar used to chart atmospheric data. Mass says they show up beautifully.

“Birds are wonderful targets," he says. "They’re much better targets than a little raindrop."

In addition to just seeing their movements on the screen (often correlating with sunrise and sunset — the birds tend to head north after dark), Mass says you can observe how certain weather phenomena influence their movements. Mass says that might explain why the birds started their big migration this past Wednesday.

“A warm front had moved through. And the winds aloft had become strong out of the south, but with little rain," he says. "So the birds got a free ride, with strong winds from the south, moving to the north that really allowed them to go faster than normal.”

Mass says many ornithologists do rely on weather service radar to keep track of seasonal migration.


Friday: Still wet and cool in the morning hours. Some snow at higher elevations before a front moves through. Then warmer, partly cloudy with temperatures in the upper 40s.

Saturday: Dry in the morning until a weak weather system arrives in the afternoon, bringing more showers. Highs in the upper 40s.

Sunday: The best day of the weekend. Sunny, with just a few clouds and temperatures near 50.

Monday-Tuesday: Dry, until showers arrive late Tuesday and continue overnight into Wednesday.

Weather with Cliff Mass airs at 9:02 a.m. Friday, right after BirdNote, and twice on Friday afternoons during All Things Considered. The feature is hosted by KNKX environment reporter Bellamy Pailthorp. Cliff Mass is a University of Washington professor of atmospheric sciences, a renowned Seattle weather prognosticator, anda popular weather blogger. You can also subscribe to podcasts of Weather with Cliff Mass shows, viaiTunes or Google Play.

Bellamy Pailthorp covers the environment for KNKX with an emphasis on climate justice, human health and food sovereignty. She enjoys reporting about how we will power our future while maintaining healthy cultures and livable cities. Story tips can be sent to