Inland Empire (Riverside–San Bernardino), CA Air Quality & Smog

Dominant pollutants, when smog is worst, notable historical episodes, and local agency resources for Inland Empire (Riverside–San Bernardino), 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, worst in summer), PM2.5 (wildfire season + winter inversions).

Seasonal pattern: when smog is worst

The Inland Empire — Riverside and San Bernardino counties east of LA — has the worst ozone pollution in the United States. The American Lung Association's 2025 State of the Air ranked the Riverside-San Bernardino metro #1 for ozone days for the 25th consecutive year. The geometry traps LA Basin pollution against the San Bernardino Mountains.

A recent or notable event

Multiple years in a row, the Inland Empire has averaged 100+ days per year with ozone above the federal standard — by far the worst record in any major US metro.

Local agencies and resources

SCAQMD covers both LA and the Inland Empire. The Crestline and Mira Loma monitors regularly post the highest readings in the country.

• South Coast AQMD
• CARB

How to check air quality in Inland Empire (Riverside–San Bernardino)

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 Inland Empire (Riverside–San Bernardino)-specific advisories and alerts that go beyond the federal AirNow feed, check the agency pages above directly.

Common questions about Inland Empire (Riverside–San Bernardino) air quality

Why does Inland Empire (Riverside–San Bernardino) have air-quality and smog problems?

The Inland Empire — Riverside and San Bernardino counties east of LA — has the worst ozone pollution in the United States. The American Lung Association's 2025 State of the Air ranked the Riverside-San Bernardino metro #1 for ozone days for the 25th consecutive year. The geometry traps LA Basin pollution against the San Bernardino Mountains.

What are the main air pollutants in Inland Empire (Riverside–San Bernardino)?

Inland Empire (Riverside–San Bernardino)'s dominant pollutants are ozone (year-round, worst in summer), PM2.5 (wildfire season + winter inversions). The AQI on any given day is usually driven by whichever of these is highest.

Has Inland Empire (Riverside–San Bernardino) had a major air-quality or smog event?

Multiple years in a row, the Inland Empire has averaged 100+ days per year with ozone above the federal standard — by far the worst record in any major US metro.

How can I check Inland Empire (Riverside–San Bernardino)'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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