What is the air quality trend in Chelmsford?

Over the past 7 days, Chelmsford had an average AQI of 72 based on station measurements. The worst day was 2026-07-17 with AQI 128.

How is Chelmsford air quality measured?

Air quality in Chelmsford 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 Chelmsford, United States

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

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

Current AQI
Good Station

48 Hours 7 Days 14 Days 20 Days

CSV JSON

Air Quality Index Station

168h

PM2.5 Station

168h · 2 stations

Temperature GFS model

27pt

Precipitation GFS model

mm/day

Daily Summary Station

Date	AQI	Range	PM2.5 avg	PM10 avg	Hours	Stations
2026-07-21	46	34–60	11.3 µg/m³	13.1	24h	9
2026-07-20	57	28–168	17.0 µg/m³	5.8	24h	10
2026-07-19	55	37–83	14.8 µg/m³	21.6	24h	11
2026-07-18	75	28–117	24.2 µg/m³	46.7	24h	10
2026-07-17	128	32–213	58.4 µg/m³	4.1	24h	11
2026-07-16	87	35–193	32.0 µg/m³	—	24h	10
2026-07-15	58	40–101	15.8 µg/m³	26.6	24h	10

Back to Chelmsford Air Quality