Insights: San Francisco-Oakland-Hayward, CA metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 21 over 20 measured days in 2025, which corresponds to a Good band and a Excellent metro-wide health grade. The monitored-day split lands at 20 Good days (100%), 0 Moderate (0%), and 0 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 29 while the highest single-day reading hit 32 (Good). Metro residents averaged roughly 30.0 clean-air days per 30-day window across the reporting year.

Across the 2020–2025 trend window, good days shifted by -130 and the median AQI moved -32 points, which classifies the multi-year trajectory as improving. The metro avoided any Unhealthy-tier days entirely, an outcome that typically reflects favorable wind patterns, lower industrial density, or effective regional emission controls. Metros with comparable AQI profiles include Bremerton-Silverdale, WA (96.2% good, AQI 21); Juneau, AK (85.1% good, AQI 21); Longview, WA (91.6% good, AQI 21).