Worst air pollution Simi Valley, today and tomorrow
Today (20 September): Air quality in Simi Valley is moderate. AQI and PM10 are moderate; PM2.5 and NO2 are fair; O3, SO2, CO, HCHO, and PM1 are good. Pollution peaks around 3:00 AM (PM10: 40.9/100).
Tomorrow (21 September 2026): Air quality in Simi Valley is fair. AQI improves to fair; PM10 decreases to fair; NO2 decreases to good; O3 increases to fair; all other pollutants stay as today. Pollution peaks around 12:00 PM (PM10: 34.3/100). Airmine updates local air quality forecasts four times daily.
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Developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team
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Simi Valley's air quality reflects partial topographic enclosure between the Santa Susana Mountains and Simi Hills, with vehicle emissions from SR-118 the primary local source. The valley receives accumulated Los Angeles basin pollution under inversions, while the Simi Pass and Santa Ana winds provide periodic flushing of valley emissions throughout the year.
Today - 20 September | Pollution peaks at 03:00
AQI:
Moderate
40.9/100
PM2.5 (fine particles):
Fair
27.0/100
PM10 (coarse particles):
Moderate
40.9/100
NO2 (nitrogen dioxide):
Fair
24.7/100
O3 (ozone):
Good
15.8/100
SO2 (sulfur dioxide):
Good
0.7/100
CO (carbon monoxide):
Good
0.4/100
HCHO (formaldehyde):
Good
1.5/100
PM1 (ultrafine particles):
Good
13.1/100
Levels show the poorest local air quality during the day
Tomorrow - 21 September | Pollution peaks at 12:00
AQI:
Fair
34.3/100
PM2.5 (fine particles):
Fair
26.4/100
PM10 (coarse particles):
Fair
34.3/100
NO2 (nitrogen dioxide):
Good
15.2/100
O3 (ozone):
Fair
23.6/100
SO2 (sulfur dioxide):
Good
0.9/100
CO (carbon monoxide):
Good
0.5/100
HCHO (formaldehyde):
Good
2.2/100
PM1 (ultrafine particles):
Good
13.2/100
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Frequently Asked Questions
Is air quality bad in Simi Valley right now?
On 20 September 2026, overall air quality in Simi Valley is moderate. AQI is the main air quality indicator at 40.9/100. Pollution peaks around 3:00 AM (PM10: 40.9/100).
Will air quality be worse tomorrow in Simi Valley?
On 21 September 2026, air quality conditions in Simi Valley will be better than today, with AQI forecast at fair at 34.3/100. Pollution peaks around 12:00 PM (PM10: 34.3/100).
When is air pollution at its worst in Simi Valley?
Air quality in Simi Valley shifts across the year — winter typically brings the cleanest stretch, once occasional rain clears the basin, whereas summer and early autumn bring the highest ozone levels, and wildfire smoke can spike particulate readings sharply from August through October. The mountains ringing the basin can trap pollution close to the ground for days when winds are calm.
Are air quality levels in Simi Valley based on measurements or forecasts?
It is forecasts derived by downscaling forecasts provided by EU’s Copernicus Atmosphere Monitoring Service (CAMS) by taking into account local conditions such as traffic patterns. CAMS bases its forecast on satellite measurements of particles and chemical compounds in the atmosphere. Airmine’s services were developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team.
Why doesn’t the forecast always reflect wildfire impacts?
Airmine’s forecast uses CAMS (Copernicus Atmosphere Monitoring Service) as its background atmospheric model. While CAMS includes wildfire emissions, these are derived from satellite observations and are not available in real time. During rapidly evolving wildfire events, there may therefore be a delay before increased emissions are incorporated into the model. As a result, the forecast may temporarily underestimate PM₂.₅ and other pollutants associated with wildfire smoke.
During rapidly evolving wildfire events, CAMS may lag by approximately 1–2 days before increased wildfire emissions are fully represented, which can lead to temporary underestimation of PM₂.₅ concentrations in Airmine’s forecast.
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Data provided by Airmine — Last update: 20 September 2026 at 14:33 CEST (Data is updated four times daily.)
This forecast is produced independently using Airmine's own atmospheric data and models.
Unless explicitly made clear, the content on this site has not been paid for by external organisations and is Airmine's sole responsibility.
Disclaimer: Forecasts are provided for informational purposes only and should not be relied upon as medical advice. Actual pollen and air quality conditions may vary from the forecast. If you have allergies, asthma, or another medical condition, consult a healthcare professional. Please see our Terms of Service for important information about limitations of liability.
Some text on this page may be generated or summarised using artificial intelligence (AI). Wherever possible, AI-generated content is enriched with Airmine's proprietary data to improve its accuracy and relevance. However, AI-generated content may still contain errors, omissions, or inaccuracies.
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