Hourly Weather | Today Tuesday, July 21, 2026
Waltham, Massachusetts
5 AM
Cloudy Night
61°
Feels Like 59°
0
Humidity: 95%
UV Index: 0
Wind: 6 mph
6 AM
Cloudy Weather
63°
Feels Like 61°
0
Humidity: 93%
UV Index: 0
Wind: 6 mph
7 AM
Cloudy Weather
64°
Feels Like 64°
0
Humidity: 92%
UV Index: 1
Wind: 7 mph
8 AM
Cloudy Weather
66°
Feels Like 68°
5
Humidity: 86%
UV Index: 2
Wind: 8 mph
9 AM
Cloudy Weather
70°
Feels Like 72°
5
Humidity: 79%
UV Index: 2
Wind: 8 mph
10 AM
Cloudy Weather
73°
Feels Like 73°
6
Humidity: 71%
UV Index: 3
Wind: 10 mph
11 AM
Cloudy Weather
75°
Feels Like 77°
7
Humidity: 63%
UV Index: 4
Wind: 12 mph
12 PM
Cloudy Weather
79°
Feels Like 79°
7
Humidity: 58%
UV Index: 4
Wind: 13 mph
1 PM
Cloudy Weather
79°
Feels Like 81°
11
Humidity: 54%
UV Index: 5
Wind: 14 mph
2 PM
Cloudy Weather
81°
Feels Like 81°
19
Humidity: 52%
UV Index: 4
Wind: 15 mph
3 PM
Cloudy Weather
79°
Feels Like 79°
19
Humidity: 57%
UV Index: 3
Wind: 15 mph
4 PM
Cloudy Weather
79°
Feels Like 77°
24
Humidity: 63%
UV Index: 2
Wind: 14 mph
5 PM
Cloudy Weather
77°
Feels Like 75°
47
Humidity: 70%
UV Index: 1
Wind: 13 mph
6 PM
Stormy Weather
75°
Feels Like 72°
51
Humidity: 77%
UV Index: 1
Wind: 12 mph
7 PM
Cloudy Weather
73°
Feels Like 75°
47
Humidity: 84%
UV Index: 0
Wind: 12 mph
8 PM
Rainy Weather
72°
Feels Like 70°
75
Humidity: 91%
UV Index: 0
Wind: 10 mph
9 PM
Rainy Weather
72°
Feels Like 68°
75
Humidity: 95%
UV Index: 0
Wind: 10 mph
10 PM
Cloudy Weather
70°
Feels Like 72°
49
Humidity: 100%
UV Index: 0
Wind: 10 mph
11 PM
Rainy Weather
70°
Feels Like 68°
75
Humidity: 98%
UV Index: 0
Wind: 10 mph

Hourly Air Quality Forecast - AQI (US EPA)

5 AM
46 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 7.74 µg/m³
  • PM10: 11.05 µg/m³
  • O3: 0.049 ppm
  • NO2: 0.5 ppb
  • SO2: 0.2 ppb
  • CO: 0.13 ppm

Health Recommendations:

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

6 AM
44 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 7.03 µg/m³
  • PM10: 10.37 µg/m³
  • O3: 0.048 ppm
  • NO2: 0.5 ppb
  • SO2: 0.2 ppb
  • CO: 0.12 ppm

Health Recommendations:

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

7 AM
43 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 6.14 µg/m³
  • PM10: 9.46 µg/m³
  • O3: 0.047 ppm
  • NO2: 0.6 ppb
  • SO2: 0.2 ppb
  • CO: 0.11 ppm

Health Recommendations:

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

8 AM
44 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 5.21 µg/m³
  • PM10: 8.48 µg/m³
  • O3: 0.047 ppm
  • NO2: 0.7 ppb
  • SO2: 0.2 ppb
  • CO: 0.11 ppm

Health Recommendations:

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

9 AM
45 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 4.46 µg/m³
  • PM10: 7.76 µg/m³
  • O3: 0.049 ppm
  • NO2: 0.7 ppb
  • SO2: 0.2 ppb
  • CO: 0.10 ppm

Health Recommendations:

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

10 AM
46 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 4.07 µg/m³
  • PM10: 7.74 µg/m³
  • O3: 0.050 ppm
  • NO2: 0.6 ppb
  • SO2: 0.2 ppb
  • CO: 0.10 ppm

Health Recommendations:

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

11 AM
46 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 4 µg/m³
  • PM10: 8.24 µg/m³
  • O3: 0.050 ppm
  • NO2: 0.4 ppb
  • SO2: 0.2 ppb
  • CO: 0.10 ppm

Health Recommendations:

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

12 PM
47 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 4.2 µg/m³
  • PM10: 8.88 µg/m³
  • O3: 0.050 ppm
  • NO2: 0.3 ppb
  • SO2: 0.2 ppb
  • CO: 0.10 ppm

Health Recommendations:

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

1 PM
46 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 4.39 µg/m³
  • PM10: 9.46 µg/m³
  • O3: 0.050 ppm
  • NO2: 0.3 ppb
  • SO2: 0.2 ppb
  • CO: 0.11 ppm

Health Recommendations:

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

2 PM
46 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 4.64 µg/m³
  • PM10: 10.12 µg/m³
  • O3: 0.050 ppm
  • NO2: 0.3 ppb
  • SO2: 0.2 ppb
  • CO: 0.13 ppm

Health Recommendations:

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

3 PM
46 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 4.88 µg/m³
  • PM10: 10.2 µg/m³
  • O3: 0.050 ppm
  • NO2: 0.3 ppb
  • SO2: 0.2 ppb
  • CO: 0.14 ppm

Health Recommendations:

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

4 PM
45 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 5.22 µg/m³
  • PM10: 10.27 µg/m³
  • O3: 0.049 ppm
  • NO2: 0.4 ppb
  • SO2: 0.2 ppb
  • CO: 0.15 ppm

Health Recommendations:

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

5 PM
45 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 5.69 µg/m³
  • PM10: 10.63 µg/m³
  • O3: 0.048 ppm
  • NO2: 0.5 ppb
  • SO2: 0.2 ppb
  • CO: 0.16 ppm

Health Recommendations:

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

6 PM
43 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 5.76 µg/m³
  • PM10: 9.65 µg/m³
  • O3: 0.046 ppm
  • NO2: 0.7 ppb
  • SO2: 0.2 ppb
  • CO: 0.18 ppm

Health Recommendations:

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

7 PM
39 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 5.3 µg/m³
  • PM10: 8 µg/m³
  • O3: 0.042 ppm
  • NO2: 0.9 ppb
  • SO2: 0.1 ppb
  • CO: 0.18 ppm

Health Recommendations:

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

8 PM
35 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 4.67 µg/m³
  • PM10: 6.94 µg/m³
  • O3: 0.037 ppm
  • NO2: 1 ppb
  • SO2: 0.1 ppb
  • CO: 0.15 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 4.21 µg/m³
  • PM10: 6.31 µg/m³
  • O3: 0.032 ppm
  • NO2: 0.9 ppb
  • SO2: 0.1 ppb
  • CO: 0.12 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 4.06 µg/m³
  • PM10: 6 µg/m³
  • O3: 0.029 ppm
  • NO2: 0.9 ppb
  • SO2: 0.1 ppb
  • CO: 0.10 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 4.18 µg/m³
  • PM10: 5.89 µg/m³
  • O3: 0.028 ppm
  • NO2: 0.9 ppb
  • SO2: 0.1 ppb
  • CO: 0.09 ppm

Health Recommendations:

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