What is the air quality trend in Boulder?

Over the past 8 days, Boulder had an average AQI of 18 based on station measurements. The worst day was 2026-09-03 with AQI 19.

How is Boulder air quality measured?

Air quality in Boulder is measured by ground-level monitoring stations that report PM2.5 and PM10 concentrations hourly. CERNS.IO aggregates readings from nearby stations and converts PM2.5 to the US EPA Air Quality Index (AQI) scale.

Air Quality History for Boulder, United States

Name: Boulder Air Quality History
Creator: CERNS.IO
License: https://creativecommons.org/licenses/by/4.0/

Historical PM2.5 and AQI trend from monitoring stations near Boulder, United States.

Current AQI
Good Station

48 Hours 7 Days 14 Days 20 Days

CSV JSON

Air Quality Index Station

164h

PM2.5 Station

164h · 40 stations

Temperature GFS model

28pt

Precipitation GFS model

mm/day

Daily Summary Station

Date	AQI	Range	PM2.5 avg	PM10 avg	Hours	Stations
2026-09-05	18	15–20	4.2 µg/m³	19.6	14h	39
2026-09-04	18	14–27	4.3 µg/m³	42.2	24h	40
2026-09-03	19	15–26	4.5 µg/m³	27.8	24h	40
2026-09-02	18	16–21	4.2 µg/m³	25.4	24h	40
2026-09-01	17	15–23	4.2 µg/m³	20.4	23h	39
2026-08-31	18	15–20	4.3 µg/m³	30.4	24h	40
2026-08-30	18	15–23	4.3 µg/m³	30.1	24h	39
2026-08-29	18	17–20	4.3 µg/m³	14.6	7h	39

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