Most days, Seattle’s air reads clean. Then August arrives, the wind shifts east, and by mid-morning, the Cascades are invisible and your eyes are burning. That’s not hypothetical. We’ve watched it happen to this region every fire season since 2015, and the monitoring data from King County confirms it. The live air quality index map above shows you where things stand right now, updated every hour from EPA monitoring stations across Seattle and King County.
The Seattle Washington live AQI map at the top of this page pulls real-time readings so you can check current conditions before you go outside or crack a window. On most days, live air quality in Seattle sits in the Good to Moderate range. But from late July through October, wildfire smoke from Eastern Washington and British Columbia can move the Seattle air quality index from 40 to 180 before noon. What the air quality index reads this morning may have nothing to do with what it reads tonight.
TL;DR Quick Answers
Live Air Quality Index AQI Map Now and Today in Seattle Washington
The live air quality index (AQI) map at the top of this page shows real-time Seattle Washington air quality readings updated every hour from EPA monitoring stations across King County. Check it before outdoor activity, especially from late July through October when wildfire smoke from Eastern Washington and British Columbia can push the AQI from Good to Unhealthy within hours.
What to know right now:
Current Seattle AQI readings fall into one of six EPA health categories: Good (0-50), Moderate (51-100), Unhealthy for Sensitive Groups (101-150), Unhealthy (151-200), Very Unhealthy (201-300), or Hazardous (301+).
Most days, Seattle sits in the Good to Moderate range. Wildfire smoke season runs July through October. That’s when today’s Seattle AQI can move fast.
Sensitive groups — children, adults over 65, and people with asthma or heart conditions — should limit outdoor exposure above AQI 100. Everyone should reduce outdoor exertion above AQI 150.
For indoor protection on high-AQI days: set your HVAC to recirculate, close windows, and run a MERV 13 filter. A standard MERV 8 does not block wildfire smoke particulates.
For the most current Seattle Washington air quality conditions, check the live map above or visit airnow.gov.
Top Takeaways
1. Wildfire smoke drives Seattle’s worst air quality events — not traffic or industry. Vehicle exhaust and wood smoke contribute to winter PM2.5, but the events that push Seattle’s AQI into Unhealthy and above are almost entirely wildfire smoke transported from Eastern Washington and British Columbia.
2. The AQI can move dramatically within a few hours. A Good reading at 8 a.m. doesn’t hold through the afternoon when smoke is active. During fire conditions, check Seattle WA AQI live updates several times per day.
3. Closing your windows alone won’t protect your indoor air. Without HVAC filtration, indoor PM2.5 still reaches 83 to 95 percent of outdoor levels in a sealed home. HVAC recirculation with a MERV 13 filter changes that number significantly.
4. Sensitive groups need to act before conditions reach the red range. The Unhealthy for Sensitive Groups category starts at AQI 101. Children, adults over 65, and people with asthma or heart conditions should already be indoors with filtered air at that threshold.
5. The 2025 wildfire season was more active than 2024 across Washington. If last year felt manageable, don’t plan on the same outcome this season. The Washington Smoke Blog confirmed elevated activity in Central and Eastern Washington in 2025, with impacts reaching Western Washington.
Table of Contents
What the Seattle AQI Map Shows Right Now
The live map tracks fine particulate matter, known as PM2.5, across monitoring stations throughout Seattle and King County. PM2.5 particles are smaller than 1/30 the width of a human hair. They reach deep into the lungs and can pass directly into the bloodstream, which makes them the primary health concern during wildfire smoke events. The air quality index (AQI) runs from 0 to 500 across six categories, each tied to specific health guidance.
Here is what each category means for Seattle residents:
Good (0-50): Air quality is satisfactory. Outdoor activity is fine for everyone.
Moderate (51-100): Acceptable for most people. Unusually sensitive individuals may want to limit prolonged outdoor exertion.
Unhealthy for Sensitive Groups (101-150): Children, adults over 65, pregnant people, and anyone with asthma or heart disease should reduce time spent outside. The Puget Sound Clean Air Agency issues air quality alerts when the AQI hits 101.
Unhealthy (151-200): Everyone may start to feel effects. King County Public Health recommends moving indoors and keeping windows closed.
Very Unhealthy (201-300): Serious health effects for the general population. Sensitive groups should stay inside.
Hazardous (301+): Emergency conditions. Seattle has reached this level during major wildfire smoke transport events.
What Causes Poor Air Quality in Seattle Washington
On a clean winter day, Seattle air pollution levels trace back to two main sources: wood smoke from home heating and diesel exhaust from freight traffic near the Port of Seattle and the I-5 and I-90 corridors. On a bad late-summer day, both of those become secondary.
The Puget Sound basin sits between the Cascades and the Olympics. When easterly winds develop during hot, dry weather, wildfire smoke from Eastern Washington, Central Washington, and British Columbia channels westward and pools in the lowlands. The geography holds it in. The air stagnates. The current air quality in Seattle, WA can climb within hours.
This is the dominant pattern we see in the data, and it’s the one that matters most for planning around pollution index readings in Seattle. Wildfire smoke isn’t a fringe event here. It’s a seasonal reality for this city.
Seattle Air Pollution Levels by Season
Seattle’s AQI today tells you one thing. The seasonal pattern tells you what to expect next month.
Winter (November through March) brings the highest baseline PM2.5 from wood-burning stoves combined with temperature inversions that trap cold air and pollutants close to the ground. Elevated winter PM2.5 levels in Seattle have historically run roughly 40 percent higher than summer baseline levels. (Source: IQAir, iqair.com)
Spring and early summer (April through June) tend to be the cleanest stretch of the year. Rain and onshore Pacific winds keep the AQI in the Good range on most days.
Late summer through fall (July through October) is the wildfire season. This is when Seattle WA AQI live updates matter most. The 2025 wildfire season across Washington state was more active than the relatively smoke-free 2024, with Central Washington bearing the most sustained smoke impacts. Western Washington, including Seattle, was not spared. (Source: Washington Smoke Blog, wasmoke.blogspot.com)
When Seattle AQI gets worse: The highest recorded pollution events in Seattle’s history came during August and September wildfire smoke transport events. The Puget Sound Clean Air Agency confirms that since 2015, the region has recorded the highest fine particle levels since monitoring began in 1980, with wildfire smoke as the primary driver. (Source: Puget Sound Clean Air Agency, pscleanair.gov)
How to Protect Your Indoor Air When Seattle AQI Is High
When Seattle smog levels today push into Unhealthy territory, outdoor air gets inside your home regardless of what you do. Studies show that without any intervention, indoor PM2.5 concentrations during wildfire events reach 49 to 76 percent of outdoor levels. Homes with open windows see that figure climb to 83 to 95 percent. (Source: Lawrence Berkeley National Laboratory, Indoor Air Quality Science Resource Bank, iaqscience.lbl.gov)
Here’s what actually reduces your exposure:
Set your HVAC system to recirculate rather than draw in outside air. King County Public Health specifically calls this out in their wildfire preparedness guidance. Close windows and doors. Run a portable HEPA air cleaner in the room where you spend the most time.
MERV filter ratings for wildfire smoke and particulates: The minimum efficiency reporting value (MERV) rating on your furnace filter matters most when smoke moves in. King County Public Health recommends MERV 11, MERV 13, or HEPA filters during smoke events. A MERV 13 filter catches the PM2.5 particles that carry the greatest health risk. A standard MERV 8, which most homes run year-round, does not provide meaningful protection against wildfire smoke particulates. (Source: King County Public Health, kingcounty.gov)
From what we see in homes across South Florida, and from the air quality data out of the Pacific Northwest, most homeowners don’t think about filter upgrades until the smoke is already inside. Getting the right filter in place before July is the move.
“We’ve seen this pattern across thousands of service calls and in the data from every major smoke season since 2015. A MERV 8 filter stops dust and pet dander. It doesn’t stop the PM2.5 particles in wildfire smoke. When Seattle AQI live updates show red or purple conditions, a MERV 13 filter running in a closed-up home is one of the most practical things a homeowner can do. The cost difference is a few dollars. The difference in what you’re breathing on an Unhealthy air day is not small.”
7 Essential Resources for Seattle Air Quality
1. EPA AirNow — Real-Time AQI for Seattle and King County
airnow.gov is the federal government’s primary source for real-time and forecast AQI data. Pull current readings by address, zip code, or neighborhood across greater Seattle. Hourly updates make this the most authoritative tool for tracking live air quality in Seattle.
2. EPA Fire and Smoke Map — Active Wildfire Smoke Tracking
fire.airnow.gov shows PM2.5 concentrations from wildfires overlaid with active fire locations. The EPA and U.S. Forest Service built this together. Use it to see when smoke from Eastern Washington or British Columbia is moving toward the Puget Sound and how long it will last.
3. Washington State Department of Ecology — Smoke Forecast and Monitoring
ecology.wa.gov provides a 5-day smoke forecast for Washington in summer and a 2-day forecast in winter. The interactive map shows real-time monitoring data from stations statewide. This is the most specific resource for tracking whether smoke is headed toward Western Washington.
4. Puget Sound Clean Air Agency — King County Air Quality Data
pscleanair.gov is the regional air quality authority for King, Kitsap, Pierce, and Snohomish counties. The annual Data Summary tracks fine particle levels, ozone, and wildfire smoke impacts by county. If you want to understand Seattle’s historical pollution trends year over year, start here.
5. King County Public Health — Wildfire Smoke Preparedness
kingcounty.gov gives Seattle-area residents step-by-step guidance for smoke events: MERV filter recommendations, DIY air cleaner instructions, and specific AQI thresholds for when to stay indoors.
6. Washington State Department of Health — Air Quality Surveillance Data
doh.wa.gov provides statewide air quality data through the Washington Tracking Network, including historical wildfire health impact records and current outdoor air quality guidance.
7. CDC — Air Quality, Health Effects, and What to Do
cdc.gov provides federal health guidance on how each AQI tier affects respiratory and cardiovascular health, with specific recommendations for children, older adults, and people with asthma or heart conditions. The clearest single source for understanding what a given AQI number means for your body.
Key Statistics on Seattle Air Quality and Wildfire Smoke
1. Since 2015, the Puget Sound region has recorded the highest fine particle levels since air quality monitoring began in 1980 — wildfire smoke is the primary driver. The Puget Sound Clean Air Agency’s annual data summaries confirm this across King, Kitsap, Pierce, and Snohomish counties. The 2025 wildfire season returned to elevated smoke conditions after a cleaner 2024.
Source: Puget Sound Clean Air Agency
2. Between 2007 and 2018, wildfire smoke pushed daily PM2.5 concentrations above 25 percent of baseline at roughly 40 percent of all EPA regulatory air monitors — for at least one month per year. The West Coast absorbed the most significant impact. For Seattle, this means the air quality failures during wildfire season aren’t accidents. They reflect a structural shift in baseline air quality driven by regional fire activity.
Source: Environmental Science and Technology, published via National Institutes of Health
3. When windows are open during a wildfire smoke event, indoor PM2.5 in homes can reach 83 to 95 percent of outdoor levels. Running a sealed, filtered home on HVAC recirculation with a MERV 13 filter cuts that to 33 to 44 percent. The gap between those two outcomes isn’t marginal. On a Hazardous air day, it’s the difference between breathing filtered air and breathing nearly everything outside.
Source: Lawrence Berkeley National Laboratory, Indoor Air Quality Science Resource Bank
Final Thoughts and Opinion
Seattle has genuinely good air quality most of the year. That’s not spin. On average days the AQI sits in the Good range, marine air keeps particulates low, and the rain clears what builds up. The problem is that average days no longer tell the whole story.
Wildfire smoke has changed the math. What used to be a few bad August days is now a threat window that runs from July through October in an active season. The long-term trend since 2015 points one direction. Public health agencies across King County are actively building plans around it. The 2025 season came in harder than 2024.
What frustrates us when we see indoor air quality situations like this: most of the health exposure is preventable. A household running the right filter with the HVAC set to recirculate during smoke events is in a completely different position than one that did nothing. The gap between those two outcomes is a filter upgrade that costs $15 to $25 and knowing one thermostat setting. That’s it.
The live Seattle AQI map on this page shows you the outdoor picture. The indoor half is up to you. We think it deserves more attention than it gets.
Frequently Asked Questions
1. What is the air quality in Seattle today?
The live map at the top of this page shows current Seattle AQI readings updated hourly from EPA and regional monitoring stations. Most days, Seattle sits in the Good to Moderate range. From late July through October, wildfire smoke from Eastern Washington and British Columbia can push the reading into Unhealthy or Very Unhealthy territory within a few hours. Check the map before any outdoor plans.
2. Where can I find a live AQI map for Seattle, Washington?
The live map at the top of this page pulls real-time data across Seattle and King County neighborhoods. For additional coverage, EPA AirNow at airnow.gov and the EPA Fire and Smoke Map at fire.airnow.gov provide the most authoritative hourly readings, including smoke transport forecasts.
3. What causes air pollution in Seattle?
During most of the year, Seattle air pollution levels come from vehicle traffic, diesel freight near the port, wood-burning stoves, and marine shipping. Late summer and fall change that picture. Easterly winds carry PM2.5 from wildfires across the Cascades and pool it in the Puget Sound basin, where the geography limits dispersal and the pollution index in Seattle can spike fast.
4. Does Seattle get smog?
Seattle sees ozone pollution on hot summer days, which is the technical definition of smog. But the events that push Seattle’s AQI into dangerous territory are driven by PM2.5 from wildfire smoke, not vehicle-based smog. The Enumclaw area in King County records the highest regional ozone levels. Citywide, wildfire particulates are the pollutant that causes the most serious air quality spikes.
5. How do I improve indoor air quality when Seattle AQI is high?
Close windows and doors. Set your HVAC to recirculate rather than draw in outside air. Upgrade your furnace filter to MERV 13, which is fine enough to capture the PM2.5 particles in wildfire smoke. Run a portable HEPA air cleaner in the room you use most. King County Public Health recommends MERV 11, MERV 13, or HEPA filters during smoke events. A standard MERV 8 filter does not meaningfully block wildfire smoke particulates.
Get the Right Filter Before Wildfire Season
When the Seattle AQI climbs into the red, your indoor air takes the hit too. We’ve helped homeowners find the right MERV rating for their system and their air quality situation. The difference between a MERV 8 and a MERV 13 is small on cost and real on protection during a high-smoke event. Do you have any questions about your HVAC filtration setup, filter sizing, or indoor air quality? We’re a call away.