Seattle Air Quality in 2025: Pollution Patterns
How air quality behaves in Seattle: the latest measured AQI, which pollutants dominate, seasonal patterns, and the local drivers of pollution.
Current Air Quality
Air quality is satisfactory, and air pollution poses little or no risk.
Seattle Air Quality in 2025
This page covers what shapes air quality in Seattle over the course of a year: the pollutants that dominate locally, how conditions typically shift between seasons, and the local emission sources behind them. Measured 2025 annual statistics are published by EPA's Air Quality System, not here, so the AQI figure below is the latest observation available when this page was published.
View Current Seattle Air Quality →Latest Measured Reading for Seattle
The most recent EPA AirNow observation for the Seattle-Bellevue-Kent Valley reporting area puts Seattle's AQI at 42 (Good), with fine particulate matter (PM2.5) as the dominant pollutant — typical for the Pacific Northwest region. Observed 3:00 AM PDT on August 9, 2026. Reported by Puget Sound Clean Air Agency.
This is a single observation captured when the page was published, not a 2025 average. For measured annual and monthly statistics, use the EPA's Air Quality System reports.
How Seattle Air Quality Shifts Through the Year
Mar–May: Usually Seattle's cleanest stretch. Mild temperatures and better atmospheric mixing keep both ozone and particulates down.
Jun–Aug: Heat and sunlight drive higher ozone and, in the West, wildfire-smoke episodes. Afternoons are typically the worst time to be outside.
Sep–Nov: Air quality generally improves as temperatures drop, though early fall can still carry wildfire smoke in the Pacific Northwest region.
Dec–Feb: Cold-air temperature inversions can trap PM2.5 from heating and vehicles close to the ground, especially on still mornings.
Seasonal patterns above describe how pollution typically behaves in this region. They are not measured 2025 averages for Seattle.
Is It Safe to Exercise Outside in Seattle?
With Seattle's AQI at 42 (Good), outdoor exercise is generally safe for most people. Conditions are good for running, cycling, and outdoor sports at any time of day.
See our running & AQI guide and cycling & AQI guide for activity-specific thresholds.
What's Causing Seattle's Air Pollution?
In Seattle, the leading pollutant is fine particulate matter (PM2.5). As part of the Pacific Northwest region, the main drivers of air pollution here are:
- •Wildfire smoke, increasingly severe in summer and fall
- •Vehicle emissions along the I-5 corridor
- •Wood-burning for residential heating
- •Industrial and port activity
Dig deeper: Seattle PM2.5 levels · Seattle ozone levels
Air Purifier & Monitor Buying Guides
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PM2.5 Levels
Fine particulate matter data →
Ozone Levels
Ground-level ozone data →
Seasonal Guides
Air quality by season →
Health Effects
Learn about air pollution impacts →
Frequently Asked Questions About Seattle Air Quality
What is the current air quality in Seattle?
The current Air Quality Index (AQI) in Seattle, WA is 42, which is considered good.
Is it safe to exercise outdoors in Seattle?
Yes, with an AQI of 42, outdoor exercise is safe for everyone in Seattle.
When is the best time of year to visit Seattle for good air quality?
Spring and early fall typically offer the best air quality in Seattle. Summer months may have elevated ozone levels, while winter can see higher PM2.5 from temperature inversions.
What causes air pollution in Seattle?
Air pollution in Seattle can come from vehicle emissions, industrial activity, construction, wildfires, and weather patterns. Local geography and seasonal factors also play a significant role.
Explore More Air Quality Data
Improve Indoor Air Quality
Even with good outdoor air in Seattle, indoor PM2.5, dust and allergens build up. A True-HEPA purifier keeps a bedroom or office consistently clean.
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