Today | Weather | Thursday, December 4, 2025

Active Weather Warnings

Dense Fog Advisory

Weather in Fort Collins, Colorado

02:29 AM

Now

14° F

Feels Like 9°

Precipitation 0 %

Wind 6 mph

Humidity 98 %

Today

Day 36°

Night 19°

Precipitation 1 %

Wind 5 mph

UV Index (0 - 11+) 2

Fort Collins Weather Forecast Updated

21 minutes ago

Last updated on December 04, 2025 at 2:08 AM

Weather Forecast History

Last Year's Weather on This Day (December 4, 2024)

Day

57°

Night

27°

Wind

4 mph

Precipitation

1 %

Air Quality in Fort Collins

NOW

22 AQI

Good air quality Dominant pollutant: O₃

Pollutant Concentrations:

PM_2.5 2.34 µg/m³

PM₁₀ 2.51 µg/m³

O₃ 0.023 ppm

NO₂ 4 ppb

SO₂ 0.1 ppb

CO 0.12 ppm

NH₃ 0.14 µg/m³

NO 0 µg/m³

PM_2.5 – Fine particles <2.5μm

PM₁₀ – Inhalable particles <10μm

O₃ – Ozone

NO₂ – Nitrogen dioxide

SO₂ – Sulfur dioxide

CO – Carbon monoxide

NH₃ – Ammonia

NO – Nitric oxide

Health Recommendations:

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

Show raw pollutant concentrations (µg/m³)

PM_2.5 – 2.34 µg/m³

PM₁₀ – 2.51 µg/m³

O₃ – 46.09 µg/m³

NO₂ – 7.59 µg/m³

SO₂ – 0.21 µg/m³

CO – 137.72 µg/m³

NH₃ – 0.14 µg/m³

NO – 0 µg/m³

View Hourly Air Quality Forecast

Weather Alerts and Warnings for Fort Collins

Moderate Expected Likely

Dense Fog Advisory

Dense Fog Advisory issued December 3 at 9:22PM MST until December 4 at 10:00AM MST by NWS Denver CO

Dec 3, 9:22 PM → Dec 4, 10:00 AM

WHAT: Visibility one quarter mile or less in dense fog.

WHERE: Eastern Larimer, Central Weld, and Morgan Counties,
including Fort Collins, Greeley, and Fort Morgan.

WHEN: Until 10 AM MST Thursday.

IMPACTS: Low visibility will make driving conditions hazardous.

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If driving, slow down, use your headlights, and leave plenty of distance ahead of you.

Updated: Dec 4, 2:08 AM Source: NWS Alert