Insights: Rapid City, SD metro. Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 48 over 181 measured days in 2025, which corresponds to a Good band and a Moderate metro-wide health grade. The monitored-day split lands at 110 Good days (61%), 70 Moderate (39%), and 1 Unhealthy-for-Sensitive-Groups (1%). The 90th-percentile AQI finished at 67 while the highest single-day reading hit 107 (USG). Metro residents averaged roughly 18.2 clean-air days per 30-day window across the reporting year.

Across the 2020–2025 trend window, good days shifted by -142 and the median AQI moved +4 points, which classifies the multi-year trajectory as worsening. 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 Brookings, SD (53.0% good, AQI 48); Charleston-North Charleston, SC (58.2% good, AQI 48); Chattanooga, TN-GA (53.9% good, AQI 48).