South Coast AQMD issues ozone advisory for inland valleys and San Bernardino Mountains during heat wave
The air district forecast unhealthy air in the San Bernardino Valley and parts of the San Bernardino Mountains through Friday, with lesser impacts in Riverside, Corona, Hemet, Lake Elsinore, Perris Valley and the Coachella Valley.
The South Coast Air Quality Management District issued an ozone advisory Aug. 24 covering much of the Inland Empire, citing a heat wave. The advisory was valid until 8 p.m. Friday.
The district said it expected a multi-day high ozone event, which it also called smog, as the heat wave set in. The advisory noted that the National Weather Service had issued its own heat-related advisory and warnings.
Where air quality was forecast to be worst
Through Friday, the district said, the Air Quality Index was likely to hit the Unhealthy level or above in the San Bernardino Valley and in part of the San Bernardino Mountains. The same forecast applied to the Santa Clarita Valley and part of the San Gabriel Valley.
A lower tier, Unhealthy for Sensitive Groups or above, was forecast daily until Friday evening for the Coachella Valley and for inland sections of the South Coast Air Basin. Riverside County locations named in the advisory were the Perris Valley and the areas around Lake Elsinore, Corona, Hemet and Riverside.
Coastal areas were expected to see less ozone, according to the advisory.
Daily pattern
Each day, the district said, index levels would rise after sunrise, peak in midafternoon and then fall.
For much of the region, the overnight and early-morning forecast was for readings in the Good to Moderate range.
The district said an update would follow if forecasts showed ozone staying high past Friday.
Recommendations
When ozone pollution is elevated, the district advised residents to monitor air quality readings and cut back on outdoor activity as needed.
It also recommended waiting until evening to run gasoline-powered yard equipment, fill up at gas stations or use household chemicals. Other steps were conserving electricity and raising the air conditioner setting.
Current readings are available on the district's app and at aqmd.gov/AQImap, the advisory said.
The district's 2026 news archive also lists heat-wave ozone advisories dated July 22 and July 30.
South Coast AQMD regulates air quality across much of four counties — Los Angeles, Orange, Riverside and San Bernardino — and its territory takes in the Coachella Valley, according to the advisory.