Today | Weather | Monday, September 21, 2026

Weather in Somerville, Massachusetts

12:59 PM
Now
Cloudy Weather
66° F
Feels Like 66°
Precipitation 1 %
Wind 10 mph
UV Index (0 - 11+) 2
Humidity 57 %
Today
Cloudy Weather
Day 68°
Night 54°
Precipitation 5 %
Wind 9 mph
UV Index (0 - 11+) 4

Somerville Weather Forecast Updated

53 minutes ago
Last updated on
Weather Forecast History
Last Year's Weather on This Day (September 21, 2025)
Cloudy Weather

Day

68°

Night

43°

Wind

7 mph

UV Index

50

Precipitation

1 %

Air Quality in Somerville

NOW
38 AQI
Good air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 2.09 µg/m³
PM10 3.7 µg/m³
O3 0.041 ppm
NO2 1.5 ppb
SO2 0.4 ppb
CO 0.17 ppm
NH3 0.05 µg/m³
NO 0.46 µg/m³
PM2.5 – Fine particles <2.5μm
PM10 – Inhalable particles <10μm
O3 – Ozone
NO2 – Nitrogen dioxide
SO2 – Sulfur dioxide
CO – Carbon monoxide
NH3 – Ammonia
NO – Nitric oxide

Health Recommendations:

Air quality is considered satisfactory, and air pollution poses little or no risk.

Show raw pollutant concentrations (µg/m³)
PM2.52.09 µg/m³
PM103.7 µg/m³
O379.78 µg/m³
NO22.81 µg/m³
SO20.92 µg/m³
CO194.46 µg/m³
NH30.05 µg/m³
NO0.46 µg/m³