Air Quality in Gresham, Oregon — Live
Live readings from PurpleAir sensors across Gresham — with free alerts the moment the air turns.
AQI 39 from 5 PurpleAir sensors · Trending down · data from PurpleAir
As of , the air quality in Gresham, Oregon is AQI 39 — Good and falling — with PM2.5 at 7.0 µg/m³, the median of 5 live PurpleAir sensors reading 38 to 52. Canairy's verdict: Breathe easy.
For scale, that PM2.5 reading is below the World Health Organization's 24-hour guideline of 15 µg/m³. The WHO figure is a daily average and this is a live reading, so read it as a sense of magnitude rather than a formal exceedance — a brief spike and a bad day are not the same thing. More on the WHO guidelines
Pollen today in Gresham: weeds pollen is the strongest of the three at a low level, from Google's pollen forecast. Canairy shows the tree, grass and weed forecast beside the air reading on every plan, including the free one.
Free to download · Live data from PurpleAir & public monitors
Live PurpleAir sensor map for Gresham and Troutdale, Fairview, Wood Village, Portland. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in Gresham
The sensors Canairy reads in Gresham are 14 AQI points apart right now, from Good to Moderate, which is the whole reason one city-wide number can mislead you: the median describes air you may not be standing in.
| From city center | AQI | Category |
|---|---|---|
| 1.5 mi N | 43 | Good |
| 2.0 mi S | 52 | Moderate |
| 4.1 mi W | 39 | Good |
| 4.4 mi NNE | 38 | Good |
| 7.6 mi NW | 39 | Good |
Gresham sits at the eastern edge of the Portland metro, immediately south of Troutdale, where the Columbia River Gorge opens out onto the valley floor. That position is most of the story of Gresham's air. The gorge runs more than eighty miles and cuts up to 4,000 feet deep through the Cascades, and when high pressure builds on the dry side of the mountains, air is squeezed through it and arrives here first. Sometimes that east wind is just cold. Sometimes it is carrying ash.
What Canairy does for Gresham
A clear verdict
Not just a number — a plain-English call for Gresham: open the windows, or keep them shut.
Smoke alerts
A push or text the moment the air crosses your threshold — and again when it clears.
A heads-up before it's bad
Trend alerts catch the air turning, so you can close up the house before the smoke settles in.
Every place you care about
Home, work, the kids' school — across Gresham or across the country, on one screen.
Gresham is where the east wind lands first
The Columbia River Gorge ends at the eastern reaches of the Portland metro, passing right by Troutdale, which borders Gresham on the north. The pressure difference between the dry east side of the Cascades and the wet west side turns that cut in the mountains into a wind tunnel, and the winds it produces reach the west end as strong easterlies. Troutdale is known for some of the windiest conditions in the Pacific Northwest — enough that local businesses have taken to putting East Wind in their names.
You can see the gradient in an ordinary forecast. During a windstorm in early February 2026 the National Weather Service put the strongest gusts from Washougal and Troutdale eastward, with Corbett already gusting over 60 mph that morning, and forecasters warned it would be very breezy out in east Multnomah County — the part of the county Gresham sits in — while the west side of the metro stayed comparatively calm. The same corridor draws very cold east winds toward the mouth of the gorge in winter, which is where the region's snow and freezing-rain events come from.
The 2017 Eagle Creek Fire was a local event out here
The fire started on September 2, 2017, when a teenager threw fireworks into Eagle Creek Canyon during an active burn ban. It went on to burn about 50,000 acres of the gorge and closed Interstate 84 from Troutdale to Hood River for weeks. Mt. Hood Community College in Gresham was the meeting point for evacuating residents, and on September 5 the Multnomah County Sheriff's Office issued Level 1 evacuation alerts for part of Troutdale, just up the road.
Smoke and up to an inch of ash fell across the Portland area on September 4 and 5, and it did not fall evenly. One account from those days described readings that ran from unhealthy in Gresham to moderate out in Beaverton on the same afternoon. That east-to-west gradient is the practical reason a metro-wide number is not much use if you live on this side of town.
In winter, the smoke is usually somebody's chimney
Oregon DEQ is direct about what drives fine-particle pollution across the Portland region: the primary source of PM2.5 is woodstoves, with cars, backyard burning, industry and commercial activity contributing on top of that. Cold snaps in Gresham are often east-wind snaps, and once the wind drops and a temperature inversion settles over the valley floor, that wood smoke stays down where people are breathing it.
DEQ names two criteria pollutants as the ones of most concern in the Portland area: ozone and fine particulate matter. They run on opposite calendars. Ozone builds on hot, sunny afternoons out of traffic and industrial emissions; fine particles peak on cold, still nights. A page that only watches one of them will tell you the air is fine half the year when it isn't.
Gresham air quality FAQ
What is the air quality in Gresham right now?
As of September 11, 2026 at 5:09 AM PDT, the air quality in Gresham, Oregon is AQI 39 — Good — with PM2.5 at 7.0 µg/m³, the median of 5 live PurpleAir sensors. Open the windows. Great for outdoor activity.
Why is there smoke in Gresham today?
Check the wind direction first. Gresham sits near the west end of the Columbia River Gorge, so when the flow turns easterly it delivers whatever is burning upriver before the rest of the metro notices. That is how the 2017 Eagle Creek Fire dropped ash and unhealthy air on east Multnomah County. If nothing is burning, a smoky evening in winter is most likely wood stoves and fireplaces — Oregon DEQ names woodstoves as the primary source of fine-particle pollution across the Portland region, and an inversion over the valley floor keeps that smoke from clearing.
Does Gresham really get different air than the rest of Portland?
On some days, yes, and the geography is why. Gresham is at the eastern edge of the metro next to the mouth of the Columbia River Gorge, so east winds and anything they carry arrive here before they reach Beaverton or Hillsboro. During the Eagle Creek Fire in September 2017 one report of the same afternoon had Gresham reading unhealthy while Beaverton was still moderate. On calm days the difference largely disappears.
What is an east wind event and why does it matter for air quality?
It is what happens when high pressure builds east of the Cascades and air pours west through the gorge toward the lower pressure on this side. The gorge acts as a wind tunnel, so the flow comes out fast and dry at the west end near Troutdale and Gresham. In winter those winds bring the cold air behind most of the region's snow and freezing rain. In late summer the same setup is what pushes wildfire smoke from the Cascades and the gorge directly over east Multnomah County.
What the AQI numbers mean
| AQI | Category | What it means for you |
|---|---|---|
| 0–50 | Good | Open the windows. Great for outdoor activity. |
| 51–100 | Moderate | Sensitive groups may want to take it slower outside. |
| 101–150 | Unhealthy for Sensitive Groups | Kids, elderly, and respiratory conditions stay closer to home. |
| 151–200 | Unhealthy | Skip outdoor exercise. Close windows. |
| 201–300 | Very Unhealthy | Limit time outside. N95 if you must go. |
| 301+ | Hazardous | Health emergency. Stay inside, run filtration if you have it. |
Canairy lets you tighten these bands if you’re more sensitive than the EPA default, so an alert can fire before the official category changes. How to read the Air Quality Index
Where these readings come from
The AQI at the top of this page is the median of the 5 curated PurpleAir sensors Canairy tracks in and around Gresham, with outliers set aside so that one sensor brought indoors — or parked beside a barbecue — cannot set the number for a whole city. Every sensor behind it is listed above with its distance and bearing from the city center. There is no black box here.
In the app, a place you save resolves the same way first. When no neighborhood sensor is reporting it falls back to the nearest EPA AirNow monitor, and anything modeled rather than measured is labelled a regional estimate rather than passed off as a sensor reading. How low-cost sensors compare to regulatory monitors
About Canairy
Canairy is free to download. The free plan covers one saved place with live readings, a plain-English verdict, and push alerts when the air crosses a threshold you choose. Paid plans add more places, faster refreshes, and SMS alerts. It is built by two parents in Sonoma County, California, who got tired of guessing whether it was safe to send the kids outside. Why we built it
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Air quality near Gresham
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