Today | Weather | Wednesday, May 20, 2026

Weather in Longmont, Colorado

11:06 PM
Now
Cloudy Night
48° F
Feels Like 46°
Precipitation 40 %
Wind 6 mph
Humidity 88 %
Today
Rainy Night
Day 55°
Night 41°
Precipitation 49 %
Wind 6 mph

Longmont Weather Forecast Updated

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

Day

72°

Night

43°

Wind

12 mph

UV Index

11

Precipitation

49 %

Air Quality in Longmont

NOW
34 AQI
Good air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 1.26 µg/m³
PM10 1.82 µg/m³
O3 0.036 ppm
NO2 1.9 ppb
SO2 0 ppb
CO 0.10 ppm
NH3 2.03 µg/m³
NO 0 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)
PM2.51.26 µg/m³
PM101.82 µg/m³
O371.2 µg/m³
NO23.52 µg/m³
SO20.03 µg/m³
CO113.76 µg/m³
NH32.03 µg/m³
NO0 µg/m³