Insights: San Jose-Sunnyvale-Santa Clara, CA metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 41 over 223 measured days in 2025, which corresponds to a Good band and a Excellent metro-wide health grade. The monitored-day split lands at 202 Good days (91%), 21 Moderate (9%), and 0 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 50 while the highest single-day reading hit 71 (Moderate). Metro residents averaged roughly 27.2 clean-air days per 30-day window across the reporting year.

Across the 2020–2025 trend window, good days shifted by +33 and the median AQI moved -11 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 Adrian, MI (77.3% good, AQI 41); Altoona, PA (71.9% good, AQI 41); Ann Arbor, MI (76.0% good, AQI 41).