Air Quality in Caldwell, Idaho — Live
Live readings from PurpleAir sensors across Caldwell — with free alerts when smoke, dust, or a winter inversion moves in.
AQI 6 from 3 PurpleAir sensors · Trending down · data from PurpleAir
As of , the air quality in Caldwell, Idaho is AQI 6 — Good and falling — with PM2.5 at 1.1 µg/m³, the median of 3 live PurpleAir sensors reading 4 to 18. 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 Caldwell: weeds pollen is the strongest of the three at a high 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 Caldwell and Nampa, Middleton, Parma, Star. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in Caldwell
The sensors Canairy reads in Caldwell agree right now — all 3 sit in the Good band, a 14-point spread — so the city-wide number is a fair description of the whole area today.
| From city center | AQI | Category |
|---|---|---|
| 3.4 mi W | 8 | Good |
| 4.7 mi ESE | 18 | Good |
| 4.7 mi ESE | 4 | Good |
Caldwell's air is calm for most of the year, but the Treasure Valley's bowl-shaped geography makes it change fast in two very different seasons. In summer, smoke from wildfires in Oregon, Idaho, and beyond can drift in and blanket the valley for days at a time, as it did again in late July 2026. In winter, the same mountains that shelter the valley trap cold, stagnant air at the surface, holding wood smoke, vehicle exhaust, and haze in place until a storm finally clears it out.
What Canairy does for Caldwell
A clear verdict
Not just a number — a plain-English call for Caldwell: 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 Caldwell or across the country, on one screen.
Caldwell sits at the bottom of a bowl
The Treasure Valley is ringed by low mountains and foothills, and in winter the valley floor cools faster than the air above it. That flips the normal order: instead of warm air near the ground rising and mixing pollution away, a layer of warmer air settles on top like a lid and traps the cold, stagnant air underneath. Idaho's Department of Environmental Quality calls this an inversion, and in the Treasure Valley it can last anywhere from a single day to more than a week, breaking only when a strong wind or a cold front finally mixes the layers back together.
Wind under about 5 miles per hour lets an inversion coast along for days, so Canyon County can string together a run of gray, hazy mornings with poor visibility even when there is no fire anywhere near the state. DEQ issues advisories through its Canyon County monitors during these stretches, and it is the same physics that shapes summer haze here: the valley holds onto whatever is in the air, whether that is wood smoke from someone's stove, exhaust off I-84, or a distant fire's plume, until the weather changes.
Wildfire smoke can arrive from fires you never hear about
Caldwell doesn't need a nearby fire to get bad air. In July 2024, the Durkee Fire ignited from a lightning strike east of the Oregon border and grew past 244,000 acres within a week, one of the largest fires in Oregon's history, pushing what Idaho DEQ meteorologist David Luft called one of the most significant, immediate smoke impacts the Treasure Valley had seen in years, even though the fire itself never crossed into Idaho.
That pattern repeated in late July 2026, when smoke settling over the valley got bad enough that Zoo Boise took precautions with its animals during a run of unhealthy air days. Canyon County's location downwind of Eastern Oregon's rangeland and forests means a fire three states away can matter more to Caldwell's air on a given week than anything burning in Idaho, which is exactly why a single regional forecast isn't enough and Canairy reads the sensors nearest to where you actually live.
A church-based air monitor is tracking Caldwell's growth
In September 2023, the Hispanic Access Foundation installed a PurpleAir sensor outside Rosa de Saron Church in Caldwell as part of El Aire que Respiramos, "The Air We Breathe," an EPA-funded project tracking pollution in twelve Latino communities nationwide over three years. The site's local coordinator, Pastor Reyna Ruano, pointed to the reason Caldwell was chosen: "Caldwell is growing. Nampa is growing. Boise is growing. There's so much traffic."
The project exists because the health stakes aren't evenly spread. The Hispanic Access Foundation cites Latino patients as twice as likely to end up in the emergency room for asthma, and Latino children as twice as likely to die from it compared to white children, with farmworkers carrying extra exposure from both field dust and vehicle exhaust along Caldwell's growing commuter corridors. It's one more reason Canyon County now has real sensor coverage instead of a single regional estimate standing in for what an entire county is breathing.
Caldwell air quality FAQ
What is the air quality in Caldwell right now?
As of September 14, 2026 at 8:14 AM PDT, the air quality in Caldwell, Idaho is AQI 6 — Good — with PM2.5 at 1.1 µg/m³, the median of 3 live PurpleAir sensors. Open the windows. Great for outdoor activity.
Why does Caldwell get smoky in the summer?
Caldwell sits downwind of Eastern Oregon's rangeland and forests, so a large fire two or three states away — like the 244,000-acre Durkee Fire that ignited from lightning in July 2024 — can fill the Treasure Valley with smoke for days without ever crossing into Idaho. Smoke returned again in late July 2026, unhealthy enough that Zoo Boise took precautions with its animals.
What is a winter inversion, and why does Caldwell get them?
An inversion happens when a layer of warmer air settles on top of the cold air sitting in the Treasure Valley, acting like a lid that traps wood smoke, vehicle exhaust, and haze at ground level. The valley's surrounding mountains make this common in winter, and an inversion can last from a single day to more than a week until a strong wind or storm mixes the air back out.
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 3 curated PurpleAir sensors Canairy tracks in and around Caldwell, 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 Caldwell
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