Weather in Boulder, Colorado

06:58 PM

Now

79° F

Feels Like 75°

Precipitation 5 %

Wind 6 mph

UV Index (0 - 11+) 4

Humidity 26 %

Today

Day 88°

Night 54°

Precipitation 25 %

Wind 10

UV Index (0 - 11+) 11

Warning: Extreme UV Index Today: 11+

Overexposure to the sun's harmful UV rays can cause sunburn and increase the risk of developing skin cancer, including melanoma. Protect yourself by wearing clothing that covers your skin, sunglasses, and a hat. Apply a broad-spectrum sunscreen with an SPF of 30 or higher every two hours, even on cloudy days. Minimize direct sun exposure during peak hours (10 AM to 4 PM) to reduce the risk.

Other:

Partly bright and clear.

Boulder Weather Forecast Updated

11 minutes ago

Last updated on September 04, 2025 6:46 PM

Air quality in Boulder

NOW

63 AQI

Moderate air quality Dominant pollutant: PM2.5

Pollutant Concentrations:

PM2.5 8.77 µg/m³

PM10 14.60 µg/m³

O₃ 55.34 ppb

NO₂ 8.24 ppb

SO₂ 0.44 ppb

CO 170.17 ppb

PM_2.5 – Fine particles <2.5μm

PM₁₀ – Inhalable particles <10μm

O₃ – Ozone

NO₂ – Nitrogen dioxide

SO₂ – Sulfur dioxide

CO – Carbon monoxide

Health Recommendations:

Air quality is currently in the acceptable range. However, sensitive individuals should be aware of potential risks from certain pollutants.

View Hourly Air Quality Forecast

Weather Alerts and Warnings for Boulder

Air Quality Alert

Air Quality Alert issued September 4 at 4:10PM MDT by NWS Denver CO

Sep 4, 4:10 PM → Sep 5, 4:00 PM

The Colorado Department of Public Health and Environment has
issued the following...

WHAT...Action Day for Multiple Pollutants.

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

WHEN...400 PM Thursday September 04 to 400 PM Friday September 05

IMPACTS...Action Day for Multiple Pollutants is now in effect for
the Front Range Urban Corridor. Hot, dry weather combined with
out-of-state wildfire smoke will allow ozone and fine particulate
concentrations to reach the Unhealthy for Sensitive Groups
category at times both Thursday and Friday. For Colorado air
quality conditions, forecasts, and advisories, visit:
https://www.colorado.gov/airquality/colorado_summary.aspx If
possible, please help us reduce pollution by limiting driving gas
and diesel-powered vehicles until at least 4 PM Friday, September
5, 2025.

HEALTH INFORMATION...If smoke is thick or becomes thick in your
neighborhood you may want to remain indoors. This is especially
true for those with heart disease, respiratory illnesses, the very
young, and older adults. Consider limiting outdoor activity when
moderate to heavy smoke is present. Consider relocating
temporarily if smoke is present indoors and is making you ill. If
visibility is less than 5 miles in smoke in your neighborhood,
smoke has reached levels that are unhealthy.

Updated: Sep 4, 6:46 PM Source: NWS Alert