Today | Weather | Wednesday, March 18, 2026
Active Weather Warnings

Weather in Simi Valley, California

03:47 AM
Now
Night
64° F
Feels Like 64°
Precipitation 7 %
Wind 6 mph
Humidity 51 %
Today
Sunny Weather
Day 95°
Night 64°
Precipitation 0 %
Wind 7 mph
UV Index (0 - 11+) 6

Simi Valley Weather Forecast Updated

36 minutes ago
Last updated on
Weather Forecast History
Last Year's Weather on This Day (March 18, 2025)
Sunny Weather

Day

68°

Night

45°

Wind

9 mph

UV Index

6

Precipitation

25 %

Air Quality in Simi Valley

NOW
73 AQI
Moderate air quality Dominant pollutant: PM2.5

Pollutant Concentrations:

PM2.5 22.99 µg/m³
PM10 33.2 µg/m³
O3 0.047 ppm
NO2 0.8 ppb
SO2 0.2 ppb
CO 0.16 ppm
NH3 0.04 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 acceptable; however, for some pollutants, there may be a moderate health concern for a very small number of people who are unusually sensitive to air pollution.

Show raw pollutant concentrations (µg/m³)
PM2.522.99 µg/m³
PM1033.2 µg/m³
O391.63 µg/m³
NO21.49 µg/m³
SO20.57 µg/m³
CO187.9 µg/m³
NH30.04 µg/m³
NO0 µg/m³

Weather Alerts and Warnings for Simi Valley

Severe Future Likely

Extreme Heat Watch

Extreme Heat Watch issued March 15 at 12:07AM PDT until March 20 at 8:00PM PDT by NWS Los Angeles/Oxnard CA
Mar 16, 8:00 PM Mar 20, 8:00 PM
WHAT: For the Heat Advisory, temperatures of 82 to 98 expected..
For the Extreme Heat Watch, dangerously hot conditions with
temperatures of 90 to 104 are possible.

WHERE: A portion of southwest California.

WHEN: For the Heat Advisory, from 10 AM to 8 PM PDT Monday. For
the Extreme Heat Watch, from Monday evening through Friday evening.

IMPACTS: There is a high risk for dangerous heat illness for
anyone, especially for the very young, the very old, those without
air conditioning, and those active outdoors. There is a high risk
for heat illness for sensitive populations including the very
young, the very old, those without air conditioning, and those
active outdoors.
+ Read More
Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors.
Updated: Mar 15, 10:20 AM Source: NWS Alert
Severe Expected Likely

Extreme Heat Warning

Extreme Heat Warning issued March 18 at 1:48AM PDT until March 20 at 8:00PM PDT by NWS Los Angeles/Oxnard CA
Mar 18, 1:48 AM Mar 20, 8:00 PM
WHAT: Dangerously hot conditions with temperatures between 96 and
104 expected.

WHERE: A portion of southwest California.

WHEN: Until 8 PM PDT Friday.

IMPACTS: There is a high risk for dangerous heat illness for
anyone, especially for the very young, the very old, those without
air conditioning, and those active outdoors.

ADDITIONAL DETAILS: Warm overnight low temperatures will
contribute to the heat risk, especially in the mountain and
foothill locations.
+ Read More
Drink plenty of fluids, stay in an air-conditioned room, stay out of the sun, and check up on relatives and neighbors. Take extra precautions when outside. Wear lightweight and loose fitting clothing. Try to limit strenuous activities to early morning or evening. Take action when you see symptoms of heat exhaustion and heat stroke.
Updated: Mar 18, 3:10 AM Source: NWS Alert