# Eugene, OR Air Quality Index (AQI) Today > Source: https://breathecheck.com/air-quality/us/oregon/eugene > Go, short outing, or stay in: a three-state verdict for Eugene, plus its own 30-day AQI trend and why smoke from the same corridor that hits Seattle reaches here later. That color and number are today's read on Eugene air quality. What they're actually deciding is smaller than the headline: the trail run up Spencer Butte, the kid's soccer practice, whether the windows stay open tonight. This page tracks the air quality Eugene has actually breathed over the past month, not just the one figure updating above. Skip the refreshing — [a text when the valley fills up](/alerts/) is the cheaper habit. ## Eugene's last 30 days, not just today One reading says nothing about the shape behind it. This page rebuilds the air quality Eugene saw over the trailing 30 days, from the same hourly AQI feed as the number above. It also carries a running count of **days above AQI 100 in the last 12 months**. IQAir and AccuWeather hand you today's number and stop there. Neither tells you whether today is a typical week or the one loud stretch a year. Eugene runs a median month of just 1,450 searches for its own air quality. Metros many times its size run fewer. ## Why is it hazy in Eugene today? Three things can make Eugene's sky look worse than the number suggests. The AQI is a 24-hour average that dilutes a rough afternoon. Smoke can sit aloft above the ground-level monitor, or the nearest station can sit miles off. Eugene sits at the south end of the Pacific Northwest smoke corridor, so its plume usually arrives later and thinner than in Seattle or Spokane. A commenter on r/Seattle summed up that gap during one regional smoke event: "Air sensor on ground, smoke up high (for now)." Another reply on the same thread put it shorter: "Sky biiiig, smoke faaar." None of that makes the haze fake. [Smoke aloft, a valley lid, an averaged reading](/why-is-the-air-bad-today/) goes through each cause. ![Bar chart of monthly US search volume for “air quality eugene” in Eugene, twelve months from Aug 2025 to Jul 2026. Peak 18,100 in Sep 2025, floor 880, a 2.5x gap between the 3,600 average and the 1,450 typical month. Bars are neutral blue-grey with the peak month in accent blue — these are search volumes, not AQI readings.](/img/eugene/inline-2.webp) *A small metro that out-searches much larger ones. Search volumes, not AQI readings — bars are neutral blue-grey with the peak month in accent blue, never EPA band colours, so demand data can never be read as a measurement of the air.* ## What is causing the bad air in Eugene? Wildfire smoke drifting down from British Columbia, eastern Washington and Oregon's own fire season is Eugene's main driver. Fine particulate matter (PM2.5) from burning vegetation dominates most bad-air days. A second, smaller mechanism runs in winter. Eugene sits in the Willamette Valley, a basin that can trap cold air and hold wood smoke close to the ground on a still night. That's the same kind of pooling that traps pollution in a mountain valley elsewhere, just gentler here, and a minor contributor next to fire season, not the dominant one. No Eugene-specific community account of either mechanism turned up in the material reviewed for this page — the smoke-corridor vernacular quoted above describes a commenter's own account in Seattle, not an Eugene resident. ## Is the air safe to breathe in Eugene today? Eugene's air is safe on Good or Moderate readings. **Go**, or keep it **short and unloaded** — the short loop up Spencer Butte instead of the summit push. **Don't go** once the color passes that. EPA's everyone-warning opens at 151, Unhealthy. 201 to 300, Very Unhealthy, is the same warning at a harsher level, not a wider group. Eugene sits at the tail end of the Pacific Northwest smoke corridor that also runs through Seattle and Spokane. A plume usually reaches here later, and thinner, than it hit those cities first — which is why checking today's own number matters more than trusting yesterday's Seattle headline. Past roughly 200, indoor plans aren't optional, whatever cleared through Seattle the day before. ## What AQI should you stay inside? Smoke reaching Eugene has usually already thinned by the time it clears Seattle and Spokane further north. That lag pulls personal thresholds down roughly one EPA band, the same direction wildfire smoke pulls thresholds anywhere. EPA calls [101–150 Unhealthy for Sensitive Groups](/aqi/) — the agency's category, not a personal ruling. A commenter on r/Seattle summed up the aloft gap during one regional event: "Air sensor on ground, smoke up high (for now)." Oregon has no published school or daycare AQI cutoff in what this project has reviewed. Washington's applies just north of here, not in Oregon; Minnesota's is the other documented one. [The two documented state thresholds](/daycare-air-quality-policy/) covers both. Individual numbers vary widely regardless of source. "I'll run in up to 110 because...error bars," wrote one r/Marathon_Training runner. An asthmatic runner logged 156 runs against AQI instead and found a lower wall, 60 — "my lungs struggle regardless of how well I've trained," even though EPA calls nothing under 100 unhealthy. Their own numbers: 87% of runs under 50 went fine, 42% between 50 and 70, just 12% past 70. Parents online tend to land near 100. Indoors, default to a portable HEPA purifier or a Corsi-Rosenthal box; one builder priced a 12x14 bedroom version at $130. A whole-house MERV-13 swap needs a static-pressure check from a licensed tech first. [Filter ratings, box fans and what they can't fix](/indoor/) covers the rest. ![Two EPA AQI colour scales for reading Eugene's number. The upper strip runs the whole index 0 to 500 in six bands, each segment as wide as the range it covers: Good 0-50 green, Moderate 51-100 yellow, Unhealthy for Sensitive Groups 101-150 orange, Unhealthy 151-200 red, Very Unhealthy 201-300 purple, Hazardous 301-500 maroon. The lower strip expands the 0-150 decision zone and marks three thresholds real readers set for themselves: AQI 60 (asthmatic runner), AQI 100 (parent / MN school), AQI 110 (runner).](/img/eugene/inline-1.webp) *EPA AirNow's own colours and breakpoints. The three marked cutoffs are not EPA guidance and not Eugene rules — each is one reader's or one institution's own line.* ## Why our number may not match what you are seeing and smelling The mismatch between Eugene's sky and its number runs two directions. A smoky sky with a calm number usually means smoke sitting aloft above the monitor, or the 24-hour average diluting a rough afternoon. A clear, still day with a moderate reading usually means ground-level ozone, formed when sunlight cooks vehicle exhaust — invisible and odorless. Neither direction means the number is wrong; it means the number and the senses are measuring different things. It's the same gap the r/Seattle commenters described, just one region over. One commenter on r/Denver flagged the identical blind spot: "spreading awareness about ozone is tough because it's mostly invisible and odorless. Telling people they're breathing in a toxic invisible gas is a sure way to kill the vibe. But it must be done!" That's the monitoring station behind today's reading — its distance from the metro centroid, and the nearby PurpleAir sensor count. A station miles off under-reports whichever side of the valley sits farthest from it. [How far a single valley station can be trusted](/methodology/) is set out in full. ## Why smoke, not city size, decides who watches the air here Smoke exposure, not population, predicts search interest for air quality Eugene. Wenatchee, Washington — population roughly 35,000 — pulls more than double Atlanta's search volume for the identical query, despite a metro roughly 180 times smaller. Eugene's own median month, 1,450, beats Fort Collins's 810 and Reno's 800 on the same logic. Eugene sits at the southern edge of the same Pacific Northwest smoke corridor that reaches Seattle and Spokane first. The same plumes reach Eugene too, arriving later and usually thinner. [Boise, on the opposite side of the corridor](/air-quality/us/idaho/boise), catches many of the same regional fires. None of the three shares Eugene's second mechanism: a valley basin that can pool cold air and wood smoke through a still winter night. ## FAQ ### What's the air quality forecast for Eugene tomorrow? Wildfire smoke can shift within hours as wind direction changes. Treat it as a direction, not a lock — recheck the morning of. ### What's the UV index in Eugene today? UV runs on its own scale, separate from AQI. A clear, low-AQI day is often the highest-UV day of the week, so a good air quality reading isn't a reason to skip sunscreen. ### Who has the worst air quality in the US right now? See [how Eugene ranks today](/) against every tracked city. Its rank moves hardest during active regional wildfire smoke. ### What is in the air in Eugene right now? That's today's specific reading. Wildfire smoke (PM2.5) dominates most bad-air days here; outside of smoke season, readings are typically low. ### Why does it smell like smoke outside in Eugene? Wildfire smoke smell means burning vegetation, often from a fire many miles north or east, drifting in on regional wind patterns. If a specific fire is active, [Whether the smoke is down at street level yet](/wildfire-smoke/) is the briefing for that.