Insights: Santa Rosa, CA metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 19 over 366 measured days in 2024, which corresponds to a Good band and a Excellent metro-wide health grade. The monitored-day split lands at 348 Good days (95%), 18 Moderate (5%), and 0 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 41 while the highest single-day reading hit 72 (Moderate). Metro residents averaged roughly 28.5 clean-air days per 30-day window across the reporting year.

Across the 2020–2024 trend window, good days shifted by +58 and the median AQI moved -17 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 (97.2% good, AQI 19); Hailey, ID (86.3% good, AQI 19); Lake Havasu City-Kingman, AZ (98.6% good, AQI 19).