Today | Weather | Friday, September 18, 2026

Weather in Simi Valley, California

05:44 PM
Now
Sunny Weather
75° F
Feels Like 73°
Precipitation 0 %
Wind 8 mph
UV Index (0 - 11+) 1
Humidity 50 %
Today
Sunny Weather
Day 77°
Night 55°
Precipitation 0 %
Wind 7 mph
UV Index (0 - 11+) 7

Simi Valley Weather Forecast Updated

46 minutes ago
Last updated on
Weather Forecast History
Last Year's Weather on This Day (September 18, 2025)
Rainy Night

Day

82°

Night

66°

Wind

5 mph

Precipitation

60 %

Air Quality in Simi Valley

NOW
45 AQI
Good air quality Dominant pollutant: O3

Pollutant Concentrations:

PM2.5 7.52 µg/m³
PM10 20.81 µg/m³
O3 0.049 ppm
NO2 0.2 ppb
SO2 0.3 ppb
CO 0.13 ppm
NH3 0 µg/m³
NO 0.03 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)
PM2.57.52 µg/m³
PM1020.81 µg/m³
O395.64 µg/m³
NO20.45 µg/m³
SO20.76 µg/m³
CO152.82 µg/m³
NH30 µg/m³
NO0.03 µg/m³