Hourly Weather | Today Wednesday, May 20, 2026
Waltham, Massachusetts
9 PM
Cloudy Night
79°
Feels Like 75°
20
Humidity: 44%
UV Index: 0
Wind: 10 mph
10 PM
Cloudy Night
75°
Feels Like 72°
20
Humidity: 48%
UV Index: 0
Wind: 10 mph
11 PM
Cloudy Night
72°
Feels Like 70°
20
Humidity: 52%
UV Index: 0
Wind: 9 mph

Hourly Air Quality Forecast - AQI (US EPA)

9 PM
33 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 5.24 µg/m³
  • PM10: 6.2 µg/m³
  • O3: 0.036 ppm
  • NO2: 3.4 ppb
  • SO2: 0.3 ppb
  • CO: 0.14 ppm

Health Recommendations:

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

10 PM
31 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 4.34 µg/m³
  • PM10: 5.06 µg/m³
  • O3: 0.033 ppm
  • NO2: 3.2 ppb
  • SO2: 0.3 ppb
  • CO: 0.14 ppm

Health Recommendations:

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

11 PM
29 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 3.2 µg/m³
  • PM10: 3.77 µg/m³
  • O3: 0.032 ppm
  • NO2: 3 ppb
  • SO2: 0.2 ppb
  • CO: 0.13 ppm

Health Recommendations:

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