Today | Weather | Wednesday, May 20, 2026

Weather in Boulder, Colorado

02:50 PM
Now
Partly Sunny with Showers
55° F
Feels Like 59°
Precipitation 55 %
Wind 6 mph
UV Index (0 - 11+) 4
Humidity 61 %
Today
Rainy Weather
Day 57°
Night 37°
Precipitation 86 %
Wind 5 mph
UV Index (0 - 11+) 3

Boulder Weather Forecast Updated

Last updated on
Weather Forecast History
Last Year's Weather on This Day (May 20, 2025)
Partly Sunny with Showers

Day

68°

Night

46°

Wind

17 mph

UV Index

11

Precipitation

49 %

Air Quality in Boulder

NOW
39 AQI
Good air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 0.92 µg/m³
PM10 1.35 µg/m³
O3 0.042 ppm
NO2 0.1 ppb
SO2 0 ppb
CO 0.08 ppm
NH3 0.57 µg/m³
NO 0.1 µg/m³
PM2.5 – 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)
PM2.50.92 µg/m³
PM101.35 µg/m³
O382.13 µg/m³
NO20.26 µg/m³
SO20.11 µg/m³
CO89.83 µg/m³
NH30.57 µg/m³
NO0.1 µg/m³