Philadelphia, PA Air Quality & Smog

Dominant pollutants, when smog is worst, notable historical episodes, and local agency resources for Philadelphia, PA — plus how to check the current AQI. For real-time readings, the free Smog Report iOS app pulls live air quality from EPA AirNow.

Dominant pollutants

ozone (summer), PM2.5 (industrial + transport).

Seasonal pattern: when smog is worst

Philadelphia's ozone elevates on hot summer days, particularly in the Delaware River corridor with its refineries. PM2.5 baseline is higher than other Northeast metros due to the I-95 + industrial mix. The June 2023 Canadian smoke event hit Philadelphia particularly hard.

A recent or notable event

June 7-8, 2023 — Philadelphia was the most-affected major US city in the June 2023 Canadian smoke episode, peaking above AQI 400.

Local agencies and resources

PA DEP runs most regulatory monitors. Philadelphia AMS operates additional city-level monitors.

• Pennsylvania DEP
• Philadelphia Air Management Services (AMS)

How to check air quality in Philadelphia

The EPA's AirNow.gov publishes the canonical reading from the nearest regulatory monitor. For glanceable iPhone access — including widgets, Live Activities, Siri voice queries, and Apple Watch — install Smog Report. It's free, requires no account, and pulls from the same AirNow API.

For Philadelphia-specific advisories and alerts that go beyond the federal AirNow feed, check the agency pages above directly.

Common questions about Philadelphia air quality

Why does Philadelphia have air-quality and smog problems?

Philadelphia's ozone elevates on hot summer days, particularly in the Delaware River corridor with its refineries. PM2.5 baseline is higher than other Northeast metros due to the I-95 + industrial mix. The June 2023 Canadian smoke event hit Philadelphia particularly hard.

What are the main air pollutants in Philadelphia?

Philadelphia's dominant pollutants are ozone (summer), PM2.5 (industrial + transport). The AQI on any given day is usually driven by whichever of these is highest.

Has Philadelphia had a major air-quality or smog event?

June 7-8, 2023 — Philadelphia was the most-affected major US city in the June 2023 Canadian smoke episode, peaking above AQI 400.

How can I check Philadelphia's air quality right now?

The EPA's AirNow.gov publishes the official reading from the nearest regulatory monitor. For live AQI on your iPhone — with home-screen widgets, Lock Screen Live Activities, Siri, and Apple Watch — the free Smog Report app pulls from the same AirNow feed. No account is required.

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