Overview
- EPA AirNow maps on Jan. 19–20 continued to show pockets of 'unhealthy' PM2.5 in parts of California, with some affected areas also reported in Oregon.
- Recent readings cited in official monitoring included Fresno at AQI 148, Arden Arcade–Del Paso Manor 113, Modesto 103 and Bakersfield 102, with Portola and Mammoth Lakes also flagged in updates.
- Health guidance urges residents to stay indoors, keep windows and doors closed, use recirculation with MERV-13 or HEPA filtration and limit outdoor exertion until conditions improve.
- Officials highlight elevated risks for children and adolescents, older adults and people with heart or lung disease, advising vigilance for symptoms such as breathing difficulty, chest discomfort and persistent cough.
- Authorities have not identified a single cause for the spike, with typical contributors cited including smoke, vehicle and industrial emissions and dust under stable, low-wind conditions.