What is the air quality in Boulder CO?

Boulder CO, United States of America has an annual US AQI of 47 (Reasonable) and average PM2.5 of 6.3 µg/m³, ranking #535 of 5856 cities. Main pollutant: O3.

What is the cleanest month in Boulder CO?

October is typically the cleanest month (AQI 37) and July the most polluted (AQI 67).

Where does Boulder CO's air quality data come from?

PM2.5: 1998–2026 (monitors 1999–2026, satellite 1998–1999, 2004, 2011–2012, 2021; 2026 provisional (AirNow)). Measured by government monitoring stations. Full sources are on the methodology page.

Boulder CO, United States of America — Air Quality & Clean City Guide 2026

Boulder CO Air Quality Data

Global rank	City	Continent	AQI	PM2.5
535	Boulder CO, United States of America	North America	AQI 47	PM2.5 6.3 µg/m³