What is the air quality trend in Chelmsford?

Over the past 15 days, Chelmsford had an average AQI of 51 based on station measurements. The worst day was 2026-07-17 with AQI 115.

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

335h

PM2.5 Station

335h · 2 stations

Temperature GFS model

56pt

Precipitation GFS model

mm/day

Daily Summary Station

Date	AQI	Range	PM2.5 avg	Hours	Stations
2026-07-22	25	25–25	6.1 µg/m³	1h	2
2026-07-21	46	28–68	11.3 µg/m³	24h	10
2026-07-20	56	28–166	16.2 µg/m³	24h	11
2026-07-19	55	33–83	14.6 µg/m³	24h	12
2026-07-18	70	28–99	21.8 µg/m³	24h	12
2026-07-17	115	38–192	51.0 µg/m³	24h	12
2026-07-16	86	40–173	30.1 µg/m³	24h	11
2026-07-15	55	30–103	14.6 µg/m³	24h	12
2026-07-14	44	37–53	10.7 µg/m³	24h	12
2026-07-13	36	24–51	8.7 µg/m³	24h	12
2026-07-12	37	25–47	8.9 µg/m³	24h	12
2026-07-11	40	32–48	9.5 µg/m³	24h	12
2026-07-10	38	28–70	9.3 µg/m³	24h	11
2026-07-09	34	24–40	8.1 µg/m³	24h	11
2026-07-08	34	26–48	8.2 µg/m³	22h	11

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