Tomorrow | Weather | Boulder, Colorado

Active Weather Warnings
Tuesday, July 21, 2026
Sunny with a Chance of Thunderstorms
Day 93°
Night 63°
Precipitation 55 %
Wind 8 mph
UV Index (0 - 11+) 11
Weather Forecast History
Last Year's Weather on This Day (July 21, 2025)
Cloudy Night

Day

97°

Night

66°

Wind

6 mph

Precipitation

1 %

Weather Alerts and Warnings for

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 20, 8:06 PM Source: NWS Alert