Most Seattle homeowners check the AQI once, in the morning, and call it done. By noon, when wildfire smoke has shifted in from eastern Washington and the reading has climbed from 42 to 118, that morning number is useless. The gap between those two readings is the difference between a safe run along the Burke-Gilman Trail and a health decision you did not know you were making.
The Air Quality Index is the EPA’s standardized scale for measuring how clean or polluted the outdoor air is at any given moment. It runs from 0 to 500. The higher the number, the greater the health concern. For Seattle residents, tracking that number in real time is not a weather hobby. It is a health decision with real consequences.
This page gives you live AQI data for Seattle, Washington, a plain-language breakdown of what the numbers mean, and direct guidance on when to act and how to protect your indoor air when the map turns orange or red.
TL;DR Quick Answers
Live Air Quality Index AQI Map Now Today in Seattle, Washington
Seattle’s live AQI updates every hour. Check airnow.gov or the Seattle AQI map for your current reading by neighborhood.
What the number means right now:
- 0–50: Good. Safe for everyone, including children and sensitive groups.
- 51–100: Moderate. Fine for most. Limit prolonged outdoor exertion if you have asthma or a heart condition.
- 101–150: Unhealthy for Sensitive Groups. Children, elderly, and anyone with respiratory or cardiovascular conditions should reduce outdoor time.
- 151–200: Unhealthy. Everyone should limit outdoor activity.
- 201+: Very Unhealthy to Hazardous. Stay inside. Close windows. Run a MERV-13 filter or HEPA air purifier.
What drives Seattle’s AQI today:
Seattle’s two dominant pollution sources are wildfire smoke from eastern Washington and British Columbia (July through October) and wood stove emissions trapped by temperature inversions (November through March). PM2.5 is the pollutant behind most AQI alerts. Neighborhoods south of downtown — Beacon Hill, South Park, the Duwamish Valley — routinely read higher than the regional average.
One number to act on: AQI 100. Below it, outdoor air in Seattle is generally safe for healthy adults. Above it, close your windows and check your filter.
Top Takeaways
- The AQI scale runs from 0 to 500. Good is 0–50. Unhealthy for Sensitive Groups starts at 101. Unhealthy for everyone starts at 151. Those two thresholds should govern every outdoor activity decision you make in Seattle during summer and fall.
- Wildfire smoke is Seattle’s dominant air quality threat. PM2.5 from fires in eastern Washington, Oregon, and British Columbia drives the majority of Seattle’s high-AQI days between July and October. The smoke does not stay east of the Cascades. Wind patterns pull it directly into the Puget Sound region, and it can arrive within hours of a fire igniting hundreds of miles away.
- Staying indoors only protects you if your filtration is right. A standard HVAC filter does not stop PM2.5. During smoke events, indoor air can carry more concentrated particulate matter than outdoor air if a MERV-13 filter or HEPA air purifier is not actively running.
- South Seattle neighborhoods face a compounded risk. Beacon Hill, South Park, and the Duwamish Valley carry chronic PM2.5 burdens from port freight and industrial activity. Wildfire smoke stacks on top of those baseline levels. If you live in these areas, your action threshold should be lower than what the regional AQI reading shows.
- AQI readings change by the hour. A morning reading tells you nothing about afternoon conditions, particularly when wind direction is shifting. Check the live map before outdoor activity — not just once at breakfast and not again until dinner.
Table of Contents
What Seattle’s Live AQI Is Telling You Right Now
The AQI Scale at a Glance
The EPA divides the AQI into six categories. Every number on the map corresponds to one of these tiers:
- 0–50 — Good. Air quality is satisfactory. No health risk for any group.
- 51–100 — Moderate. Acceptable for most people. Unusually sensitive individuals may want to limit prolonged outdoor exertion.
- 101–150 — Unhealthy for Sensitive Groups. Children, the elderly, and people with asthma, heart disease, or respiratory conditions should reduce extended outdoor activity.
- 151–200 — Unhealthy. Everyone may experience health effects. Sensitive groups face serious risk.
- 201–300 — Very Unhealthy. Health alert. Significant risk for the entire population.
- 301–500 — Hazardous. Emergency conditions. Avoid all outdoor activities.
For context on how this scale was developed and how it compares internationally, the Wikipedia entry on the Air Quality Index covers the methodology behind the numbers.
What’s Driving Seattle’s AQI Today
Seattle’s air runs on two distinct pollution cycles. From November through March, wood smoke from home heating and temperature inversions trap particulate matter in the Puget Sound basin, pushing PM2.5 levels well above summer norms. From July through October, the calculus flips. Wildfire smoke from eastern Washington, Oregon, and British Columbia becomes the dominant threat. A single wind shift can send the AQI from 35 to 160 in under six hours.
The neighborhoods that spike hardest are not random. Beacon Hill, South Park, Georgetown, and the Duwamish Valley carry chronic pollution burdens from port freight traffic and industrial activity year-round. During wildfire events, those baseline levels compound. If you live or work south of downtown, your real-world exposure is routinely higher than what the regional AQI reading shows.
Understanding PM2.5 — The Pollutant That Matters Most
PM2.5 is fine particulate matter measuring less than 2.5 microns in diameter — less than one-thirtieth the width of a single human hair. These particles are small enough to bypass your upper respiratory defenses, penetrate deep into lung tissue, and enter the bloodstream. Short-term exposure at elevated concentrations causes eye irritation, headaches, and shortness of breath. Repeated exposure is linked to cardiovascular disease, reduced lung function, and premature death.
PM2.5 drives Seattle’s AQI alerts. When the map turns orange, red, or purple, PM2.5 is almost always the reason.
When to Close Your Windows in Seattle
The action threshold is AQI 100. Below that number, outdoor air in Seattle is generally acceptable for healthy adults. At 101 and above:
- Close windows and doors, especially at night when smoke settles
- Run your HVAC system with a MERV-13 or higher filter installed
- Use a portable HEPA air purifier in bedrooms and high-use rooms
- Check the AQI hourly during wildfire events — conditions shift fast, and morning readings do not reflect afternoon reality
A standard 1-inch fiberglass filter does not stop PM2.5. It protects your equipment. It does not protect your lungs. If your filter rates below MERV-13, your system is recirculating outdoor smoke particles through your home on every cycle.
“A MERV-8 filter during a Seattle smoke event gives your lungs about as much protection as cracking a window — the particles doing the real damage are invisible, odorless, and moving straight through it, which is why the homeowners who make it through wildfire season without a health consequence are the ones who upgraded their filter rating before the map turned red, not after.”
Essential Resources
1. EPA AirNow — Real-Time Air Quality Data
The federal government’s official AQI monitoring platform. Use it to verify current readings across King County monitoring stations, including Beacon Hill and South Seattle, before making any health decision based on a third-party map.
2. EPA AirNow — AQI Basics and Health Categories
The complete AQI scale from 0 to 500, with the health category and color code for every tier. Read this before you read any map. The color means nothing if you do not know what it is telling you to do.
https://www.airnow.gov/aqi/aqi-basics
3. EPA — Indoor Air Quality
When outdoor AQI climbs, your indoor air follows — unless you have the right filtration running. This EPA resource covers the ventilation, filtration, and behavioral steps that protect your home during smoke events. Start here if you are preparing for wildfire season and have not upgraded your filter.
https://www.epa.gov/indoor-air-quality-iaq
4. Washington State Department of Ecology — Wildfire Smoke
State-level tracking and guidance on smoke events across Washington, including real-time smoke forecasts, historical event data, and health advisories for the Puget Sound region. When fires ignite east of the Cascades, check this before AirNow. It moves faster.
https://ecology.wa.gov/air-climate/air-quality/smoke-fire/wildfire-smoke
5. Washington State Department of Ecology — Air Quality Data Summary
Annual monitoring data for King, Pierce, and Snohomish Counties, including PM2.5 levels by site and the breakdown of Good, Moderate, and Unhealthy days per year. This is the most direct accounting of how Seattle’s air quality has shifted since 2015.
https://pscleanair.gov/615/Data-Summary
6. Washington State Department of Health — Air Quality Data
Health-focused air quality tracking for Washington State, connecting PM2.5 exposure to asthma rates and cardiovascular outcomes in King County. If someone in your household has a respiratory condition, this resource belongs in your bookmarks year-round.
https://doh.wa.gov/data-and-statistical-reports/washington-tracking-network-wtn/air-quality
Statistics That Put Seattle’s Air Quality in Context
1. Seattle averages approximately 14 unhealthy pollution days per year — more than four times the EPA’s recommended allowable limit of 3.2 unhealthy days per pollutant.
The EPA’s benchmark allows no more than 3.2 unhealthy days annually for PM2.5 and the same for ozone. Seattle exceeds both. For a city whose daily average AQI often registers as “Good,” the spike days tell the real story. Those spikes are the days that send sensitive residents to emergency rooms.
Source: pscleanair.gov/615/Data-Summary
2. Americans spend approximately 90 percent of their time indoors, where pollutant concentrations are often 2 to 5 times higher than outdoor levels.
This single fact reframes what a high-AQI day actually means for your family. Staying inside is the right instinct. But without a MERV-13 filter or HEPA air purifier actively removing PM2.5 from your indoor air, staying inside during a smoke event can expose you to more concentrated particulate matter than you would encounter outside. Your home is only as protective as your filtration system allows it to be.
Source: epa.gov/report-environment/indoor-air-quality
3. In 2024, King County experienced approximately 28 percent of days in the Moderate AQI category, plus 4 days classified as Unhealthy for Sensitive Groups due to elevated ozone.
The 2024 data from the Puget Sound Clean Air Agency is a useful baseline. An unusually smoke-free wildfire season kept fine particle levels low, but elevated ozone still pushed the county into the Unhealthy for Sensitive Groups category four times. In a typical wildfire year, that number climbs well above 20. The 2024 season was the exception — not what you should plan around.
Final Thoughts and Opinion
Seattle’s air quality reputation does not match Seattle’s air quality reality. The city averages “Good” on an annual basis, and that number creates a false sense of security. What it hides is the spike problem — the concentrated runs of days in late summer and early fall when wildfire smoke turns the Puget Sound basin into one of the most polluted airsheds in the country. On October 18 and 19, 2022, Seattle carried the worst air quality of any major city in the world. That is not a footnote. It is the central fact every homeowner in King County should know before wildfire season starts.
The response to that fact is preparation, not anxiety. Know your AQI threshold for action. Get a MERV-13 filter into your HVAC system before wildfire season begins, not during it. Put a HEPA air purifier in the bedroom your family sleeps in. Check the live map hourly when conditions are active. The tools to protect your household cost less than most people assume. What separates a protected household from an unprotected one during a Seattle smoke event is, most of the time, a filter upgrade and a habit.
Frequently Asked Questions
1. What is a good AQI for Seattle?
An AQI of 0–50 is classified as Good by the EPA and poses no health risk for any group. Seattle frequently hits readings in this range from late October through June, when rain and westerly winds clear out pollutants. The number to watch is 100. Above that threshold, children, the elderly, and anyone with asthma, heart disease, or a respiratory condition should limit time outdoors.
2. How often does Seattle experience bad air quality days?
Seattle averages approximately 14 unhealthy pollution days per year, split roughly between high PM2.5 days and high ozone days. Most fall between July and October, driven by wildfire smoke from regional fires. In severe wildfire years — 2018, 2020, and 2022 are the most documented — Seattle experienced multiple consecutive days of Very Unhealthy and Hazardous conditions. The 2024 wildfire season was unusually mild for Western Washington. Do not plan around it.
3. What causes poor air quality in Seattle?
Two sources dominate. From summer through early fall, wildfire smoke from fires east of the Cascades and in British Columbia drives AQI spikes, with PM2.5 as the dominant pollutant. Year-round, vehicle emissions and port freight traffic contribute to ozone and nitrogen dioxide, with the Duwamish Valley and South Park carrying the heaviest chronic exposure. From November through February, wood stove smoke trapped by temperature inversions pushes PM2.5 levels across the Puget Sound basin well above summer norms.
4. Should I stay inside when Seattle’s AQI is above 100?
Yes — with one condition you cannot skip. Staying inside during a high-AQI event is the right call. But your home is only as clean as your filter allows. A MERV-13 or higher-rated filter is required to capture PM2.5-sized particles. If your system runs a standard MERV-8 or lower filter, it is pulling outdoor smoke particles through your home on every cycle. Add a portable HEPA air purifier in rooms where your family spends the most time, starting with bedrooms.
5. How do I read the Seattle AQI map?
Color is your fastest signal. Green is Good (0–50). Yellow is Moderate (51–100). Orange is Unhealthy for Sensitive Groups (101–150). Red is Unhealthy for everyone (151–200). Purple is Very Unhealthy (201–300). Maroon is Hazardous (301 and above). Click any sensor point for the specific numerical reading and the dominant pollutant at that station. When South Seattle stations diverge significantly from the regional average, trust the local reading. The Duwamish Valley routinely registers higher than downtown monitors show.
Ready to Protect Your Home Before the Next Smoke Event?
By the time Seattle’s AQI map turns orange, most homeowners are already behind. MERV-13 filtration is the most effective single change you can make to your indoor air quality before wildfire season begins. It needs to be installed and running before the smoke arrives — not ordered the day the map turns red.
BreezioHVAC helps homeowners identify the right filter for their system, confirm whether their current setup can handle upgraded filtration, and take the steps that actually protect indoor air quality when outdoor AQI climbs. One clear recommendation. No guesswork.
Efficient Comfort. Cleaner Tomorrow.