Gresham pollen forecast - today, tomorrow and the week ahead

Currently, there is no significant pollen in Gresham.

On 26 June 2026, pollen conditions in Gresham will be similar to today with no significant pollen expected.

According to the five-day outlook, grass pollen levels will increase later in the week.

On 25 June 2026, there are no significant pollen types in Gresham.

Gresham's pollen season opens with alder from January, followed by birch and Douglas fir through March and April. Grass pollen peaks through June and July. The Columbia River Gorge channels easterly winds that can concentrate pollen across the Portland metro area, while surrounding Pacific Northwest woodland and Willamette Valley farmland contribute substantial tree and grass pollen. Frequent Pacific rainfall provides regular interruptions throughout the season.

The Gresham pollen forecast is updated four times daily. See the timestamp below for the most recent update.

Studies show that most pollen exposure (often 70–90%) comes from nearby sources, such as local trees and vegetation. A good pollen forecast therefore depends on accurately representing local vegetation. Pollen can travel long distances, but this usually matters only early in the season or during specific wind events.

Pollen data is often misunderstood. Most "pollen levels" are not real-time measurements, but forecasts.

Direct pollen measurements are typically delayed by 1-2 days because they require manual analysis. To show current conditions in Gresham, modern forecasts combine recent measurements, weather data, and information about local vegetation.

This allows us to estimate pollen levels for today and the coming days, not just report the past.

Airmine’s atmospheric monitoring platform was developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team, using satellite and Earth observation technologies to improve emissions monitoring.