Hourly Weather | Today Tuesday, July 21, 2026
Active Weather Warnings
Longmont, Colorado
2 AM
Cloudy Night
75°
Feels Like 72°
0
Humidity: 52%
UV Index: 0
Wind: 8 mph
3 AM
Cloudy Night
73°
Feels Like 70°
0
Humidity: 57%
UV Index: 0
Wind: 8 mph
4 AM
Cloudy Night
72°
Feels Like 68°
0
Humidity: 61%
UV Index: 0
Wind: 8 mph
5 AM
Cloudy Night
70°
Feels Like 66°
0
Humidity: 64%
UV Index: 0
Wind: 8 mph
6 AM
Cloudy Weather
68°
Feels Like 64°
0
Humidity: 68%
UV Index: 0
Wind: 8 mph
7 AM
Cloudy Weather
70°
Feels Like 70°
0
Humidity: 65%
UV Index: 1
Wind: 8 mph
8 AM
Cloudy Weather
73°
Feels Like 73°
2
Humidity: 59%
UV Index: 2
Wind: 9 mph
9 AM
Cloudy Weather
75°
Feels Like 77°
2
Humidity: 54%
UV Index: 4
Wind: 9 mph
10 AM
Cloudy Weather
81°
Feels Like 82°
3
Humidity: 47%
UV Index: 5
Wind: 9 mph
11 AM
Cloudy Weather
82°
Feels Like 90°
4
Humidity: 41%
UV Index: 8
Wind: 8 mph
12 PM
Cloudy Weather
86°
Feels Like 93°
4
Humidity: 37%
UV Index: 10
Wind: 7 mph
1 PM
Cloudy Weather
90°
Feels Like 97°
7
Humidity: 33%
UV Index: 11
Wind: 8 mph
2 PM
Cloudy Weather
91°
Feels Like 95°
13
Humidity: 29%
UV Index: 10
Wind: 14 mph
3 PM
Cloudy Weather
95°
Feels Like 97°
13
Humidity: 25%
UV Index: 8
Wind: 15 mph
4 PM
Cloudy Weather
97°
Feels Like 97°
17
Humidity: 24%
UV Index: 5
Wind: 15 mph
5 PM
Cloudy Weather
95°
Feels Like 93°
47
Humidity: 25%
UV Index: 4
Wind: 16 mph
6 PM
Sunny with a Chance of Thunderstorms
93°
Feels Like 88°
51
Humidity: 28%
UV Index: 2
Wind: 15 mph
7 PM
Cloudy Weather
91°
Feels Like 88°
47
Humidity: 31%
UV Index: 1
Wind: 15 mph
8 PM
Cloudy Weather
88°
Feels Like 84°
20
Humidity: 35%
UV Index: 0
Wind: 15 mph
9 PM
Cloudy Night
84°
Feels Like 81°
20
Humidity: 42%
UV Index: 0
Wind: 14 mph
10 PM
Cloudy Night
81°
Feels Like 79°
20
Humidity: 48%
UV Index: 0
Wind: 14 mph
11 PM
Cloudy Night
79°
Feels Like 75°
20
Humidity: 53%
UV Index: 0
Wind: 13 mph

Hourly Air Quality Forecast - AQI (US EPA)

2 AM
23 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 3.26 µg/m³
  • PM10: 3.48 µg/m³
  • O3: 0.025 ppm
  • NO2: 2.2 ppb
  • SO2: 0 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

3 AM
22 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 3.22 µg/m³
  • PM10: 3.45 µg/m³
  • O3: 0.024 ppm
  • NO2: 2.2 ppb
  • SO2: 0 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

4 AM
22 AQI
Good air quality Dominant pollutant: O3
Details

Pollutant Concentrations:

  • PM2.5: 3.21 µg/m³
  • PM10: 3.45 µg/m³
  • O3: 0.024 ppm
  • NO2: 2 ppb
  • SO2: 0.1 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 3.23 µg/m³
  • PM10: 3.48 µg/m³
  • O3: 0.024 ppm
  • NO2: 1.9 ppb
  • SO2: 0.1 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 3.6 µg/m³
  • PM10: 3.86 µg/m³
  • O3: 0.025 ppm
  • NO2: 1.9 ppb
  • SO2: 0.1 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 3.61 µg/m³
  • PM10: 3.88 µg/m³
  • O3: 0.025 ppm
  • NO2: 2.2 ppb
  • SO2: 0.1 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 3.05 µg/m³
  • PM10: 3.34 µg/m³
  • O3: 0.026 ppm
  • NO2: 2.1 ppb
  • SO2: 0.1 ppb
  • CO: 0.09 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 3.04 µg/m³
  • PM10: 3.36 µg/m³
  • O3: 0.028 ppm
  • NO2: 1.8 ppb
  • SO2: 0.1 ppb
  • CO: 0.10 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 1.97 µg/m³
  • PM10: 2.55 µg/m³
  • O3: 0.040 ppm
  • NO2: 0.5 ppb
  • SO2: 0.2 ppb
  • CO: 0.07 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 1.85 µg/m³
  • PM10: 2.37 µg/m³
  • O3: 0.041 ppm
  • NO2: 0.2 ppb
  • SO2: 0.2 ppb
  • CO: 0.06 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 1.91 µg/m³
  • PM10: 2.39 µg/m³
  • O3: 0.041 ppm
  • NO2: 0.2 ppb
  • SO2: 0.1 ppb
  • CO: 0.06 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 1.99 µg/m³
  • PM10: 2.46 µg/m³
  • O3: 0.041 ppm
  • NO2: 0.1 ppb
  • SO2: 0.1 ppb
  • CO: 0.06 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 1.96 µg/m³
  • PM10: 2.38 µg/m³
  • O3: 0.041 ppm
  • NO2: 0.1 ppb
  • SO2: 0.1 ppb
  • CO: 0.06 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 1.8 µg/m³
  • PM10: 2.18 µg/m³
  • O3: 0.041 ppm
  • NO2: 0.1 ppb
  • SO2: 0.1 ppb
  • CO: 0.06 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 1.62 µg/m³
  • PM10: 1.98 µg/m³
  • O3: 0.041 ppm
  • NO2: 0.1 ppb
  • SO2: 0.1 ppb
  • CO: 0.06 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 1.48 µg/m³
  • PM10: 1.85 µg/m³
  • O3: 0.042 ppm
  • NO2: 0.1 ppb
  • SO2: 0.1 ppb
  • CO: 0.06 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 1.47 µg/m³
  • PM10: 1.89 µg/m³
  • O3: 0.042 ppm
  • NO2: 0.1 ppb
  • SO2: 0.1 ppb
  • CO: 0.06 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: 1.6 µg/m³
  • PM10: 2.11 µg/m³
  • O3: 0.042 ppm
  • NO2: 0.2 ppb
  • SO2: 0.1 ppb
  • CO: 0.06 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 1.76 µg/m³
  • PM10: 2.31 µg/m³
  • O3: 0.041 ppm
  • NO2: 0.4 ppb
  • SO2: 0.1 ppb
  • CO: 0.07 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 1.95 µg/m³
  • PM10: 2.51 µg/m³
  • O3: 0.040 ppm
  • NO2: 0.5 ppb
  • SO2: 0.1 ppb
  • CO: 0.07 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 2.07 µg/m³
  • PM10: 2.58 µg/m³
  • O3: 0.038 ppm
  • NO2: 0.6 ppb
  • SO2: 0.1 ppb
  • CO: 0.07 ppm

Health Recommendations:

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

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

Pollutant Concentrations:

  • PM2.5: 2.12 µg/m³
  • PM10: 2.59 µg/m³
  • O3: 0.036 ppm
  • NO2: 0.8 ppb
  • SO2: 0.1 ppb
  • CO: 0.08 ppm

Health Recommendations:

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

Weather Alerts and Warnings for Longmont

Air Quality Alert

Air Quality Alert issued July 20 at 4:10PM MDT by NWS Denver CO
Jul 20, 4:10 PM Jul 21, 4:00 PM
The Colorado Department of Public Health and Environment has
issued the following...

WHAT...Ozone Action Day Alert.

WHERE...Douglas, Jefferson, Denver, western Arapahoe, western
Adams, Broomfield, Boulder, Larimer, and Weld Counties

WHEN...400 PM Monday July 20 to 400 PM Tuesday July 21

IMPACTS...Ozone Action Day Alert is now in effect for the Front
Range Urban Corridor. Hot and stagnant weather conditions will
result in ozone concentrations reaching the Unhealthy for
Sensitive Groups category both Monday and Tuesday during the
afternoon and evening hours. For Colorado air quality conditions,
forecasts, and advisories, visit:
https://www.colorado.gov/airquality/colorado_summary.aspx If
possible, please help us reduce ozone pollution by limiting
driving gas and diesel-powered vehicles until at least 4 p.m.
Tuesday, July 21, 2026. Colorado is also addressing ozone
pollution through state policies. For more information about
health impacts and how ozone pollution forms in Colorado, visit:
https://cdphe.colorado.gov/ozone- pollution-and-your-health

HEALTH INFORMATION...Increasing likelihood of respiratory symptoms
and breathing discomfort in active children and adults and people
with lung disease, such as asthma. Active children and adults, and
people with lung disease, such as asthma, should reduce prolonged
or heavy outdoor exertion.
Updated: Jul 21, 12:34 AM Source: NWS Alert