Air Quality in Wilmington, Delaware — Live
Live readings from PurpleAir sensors across Wilmington — with free alerts when summer ozone or a refinery incident pushes the air into unhealthy territory.
AQI 28 from 5 PurpleAir sensors · Trending down · data from PurpleAir
As of , the air quality in Wilmington, Delaware is AQI 28 — Good and falling — with PM2.5 at 5.1 µg/m³, the median of 5 live PurpleAir sensors reading 22 to 56. 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
Free to download · Live data from PurpleAir & public monitors
Live PurpleAir sensor map for Wilmington and Newark, New Castle, Claymont, Elsmere. Every dot is a real sensor, color-coded by current air quality.
Sensor by sensor in Wilmington
The sensors Canairy reads in Wilmington are 34 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 |
|---|---|---|
| 1.8 mi NNW | 31 | Good |
| 2.2 mi SSE | 41 | Good |
| 3.0 mi S | 22 | Good |
| 3.1 mi SSW | 56 | Moderate |
| 4.5 mi WSW | 26 | Good |
Wilmington's air is unremarkable most of the year — no wildfire smoke season, no dust storms, nothing dramatic. The real story here is ground-level ozone. New Castle County spent years bundled into the Philadelphia-Wilmington-Atlantic City ozone nonattainment area, reclassified from Moderate to Serious for the 2015 federal ozone standard in July 2024, before EPA split the county out into its own, smaller nonattainment area in June 2026 after three straight years of cleaner monitoring data. Summer heat and highway traffic still push some afternoons into Code Orange territory, and the state's own busiest air monitor — the National Core (NCore) station sited right in the city — tends to record the highest pollution readings anywhere in Delaware.
What Canairy does for Wilmington
A clear verdict
Not just a number — a plain-English call for Wilmington: open the windows, or keep them shut.
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A heads-up before it's bad
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Wilmington's ozone problem is decades old — and finally easing
For years, New Castle County's ozone numbers were judged as part of the sprawling Philadelphia-Wilmington-Atlantic City nonattainment area, and in July 2024 the EPA reclassified that whole region from Moderate to Serious under the 2015 8-hour ozone standard — a downgrade that comes with stricter permitting and planning rules. Two years later, in June 2026, EPA approved Delaware's request to split New Castle County out as its own nonattainment area and issued a Clean Data Determination after the county recorded three consecutive years of ozone readings meeting the federal standard.
None of that means ozone season is over. Ground-level ozone forms when tailpipe and industrial emissions cook in sunlight and heat, so Wilmington's worst air still shows up on the same still, hot summer afternoons it always has. DNREC calls Code Orange and occasionally Code Red Air Quality Action Days through the warm months, and the agency's own advice — limit outdoor exertion, drive less, wait until evening to mow the lawn — is aimed at exactly those days.
The Delaware City Refinery is the other half of the story
South of Wilmington, the Delaware City Refinery — owned by PBF Energy — has racked up more than 50 environmental violations over the past decade. In May 2025, a mechanical failure knocked out a pollution control device and the refinery released sulfur dioxide well above its permit limit, at one point reporting emissions as high as 1,450 pounds per hour, for roughly two and a half weeks before repairs were finished.
More than 86,000 people live within five miles of the refinery, and over half of them are people of color, which is why local residents and state Rep. Larry Lambert have pushed legislation to raise Delaware's pollution fines — some untouched since 1973 — to as much as $30,000 per violation. Unlike ozone, a refinery upset can happen in any season and often shows up as a sharp, short spike rather than a slow summer buildup.
Why one 'Wilmington AQI' number hides a lot
Delaware's densest cluster of monitoring stations sits in New Castle County — seven of the state's eleven permanent sites — and the NCore station in Wilmington itself is an urban site that typically posts the highest pollution readings in Delaware simply because it sits closest to traffic and industry. A leafy neighborhood like Greenville and a refinery-adjacent stretch near Claymont are not breathing the same air on the same afternoon, even though both round up to one citywide number on most apps.
That's why Canairy reads the network of PurpleAir sensors scattered across Wilmington and New Castle County instead of a single distant monitor — the reading you see is pulled from sensors near the places you actually saved, whether that's a home in Elsmere or a school near the Christina River.
Wilmington air quality FAQ
What is the air quality in Wilmington right now?
As of November 2, 2026 at 10:58 AM EST, the air quality in Wilmington, Delaware is AQI 28 — Good — with PM2.5 at 5.1 µg/m³, the median of 5 live PurpleAir sensors. Open the windows. Great for outdoor activity.
Why does Wilmington get smoggy in summer?
Ground-level ozone forms when vehicle and industrial emissions react with sunlight and heat, and New Castle County's hot, still summer afternoons are the classic recipe. The county was part of the Philadelphia-Wilmington-Atlantic City ozone nonattainment area for years before EPA split it out on its own in June 2026, and DNREC still calls Code Orange Air Quality Action Days on the worst summer days.
Does the Delaware City Refinery affect Wilmington's air?
It can. The PBF Energy-owned refinery south of the city has had more than 50 violations in the past decade, including a 2025 sulfur dioxide release that ran for roughly two and a half weeks. Refinery incidents tend to show up as sharp, short spikes rather than the slow summer buildup typical of ozone.
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 Wilmington, 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 Wilmington
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