Los Angeles, CA Air Quality & Smog

Dominant pollutants, when smog is worst, notable historical episodes, and local agency resources for Los Angeles, CA — 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 (year-round but worst June-October), PM2.5 (wildfire season).

Seasonal pattern: when smog is worst

The LA Basin's mountain-and-marine geometry traps pollutants. Summer ozone peaks midday in the eastern San Gabriel Valley (Redlands, San Bernardino) — often 50% higher than the coast. Wildfire smoke from the Sierra and Angeles foothills routinely closes schools.

A recent or notable event

The 2025 Palisades and Eaton fires in January burned during a Santa Ana wind event, pushing LA-area AQI well above 200 across much of the basin and forcing widespread school closures.

Local agencies and resources

SCAQMD runs both the regulatory monitor network and a public alert system. SCAQMD's aqmd.gov has the most-granular regional read.

• South Coast Air Quality Management District (SCAQMD)
• California Air Resources Board (CARB)

How to check air quality in Los Angeles

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

Common questions about Los Angeles air quality

Why does Los Angeles have air-quality and smog problems?

The LA Basin's mountain-and-marine geometry traps pollutants. Summer ozone peaks midday in the eastern San Gabriel Valley (Redlands, San Bernardino) — often 50% higher than the coast. Wildfire smoke from the Sierra and Angeles foothills routinely closes schools.

What are the main air pollutants in Los Angeles?

Los Angeles's dominant pollutants are ozone (year-round but worst June-October), PM2.5 (wildfire season). The AQI on any given day is usually driven by whichever of these is highest.

Has Los Angeles had a major air-quality or smog event?

The 2025 Palisades and Eaton fires in January burned during a Santa Ana wind event, pushing LA-area AQI well above 200 across much of the basin and forcing widespread school closures.

How can I check Los Angeles'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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