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.

Live Wilmington AQI from nearby PurpleAir sensors loads when this page opens in a browser, along with a live sensor map covering Wilmington and Newark, New Castle, Claymont, Elsmere.

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.

Canairy watches the sensors around your home, your kids' school, and everywhere else you care about, and tells you in plain English when the air changes enough to matter.

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, DE right now?

This page shows the current AQI for Wilmington, calculated from PurpleAir sensors across the city and New Castle County and updated continuously. The map below shows every live sensor, so you can check the reading closest to your own neighborhood.

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 AQI level is unhealthy?

Under the US EPA scale, AQI 0-50 is Good and 51-100 is Moderate. From 101 the air is Unhealthy for Sensitive Groups - kids, older adults, and people with asthma or heart conditions - and above 150 it's Unhealthy for everyone. Canairy translates these numbers into a plain-English verdict, like whether to close the windows or move a workout indoors.

Is Canairy free?

Yes. The Canairy app is free to download and includes live air quality for all your saved places, plain-English verdicts, and free push alerts when the air crosses your threshold. A paid plan adds extras like SMS text alerts.

Where does Canairy's Wilmington data come from?

Readings come from PurpleAir's network of laser particle sensors across Wilmington and surrounding New Castle County towns, cross-referenced with government monitors and the Google Air Quality API. You can see every sensor behind your numbers on the live map - there's no black box.

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