Worst air pollution Pasadena, California, today and tomorrow
Today (20 September): Air quality in Pasadena, California is moderate. AQI, PM2.5, and PM10 are moderate; NO2 is fair; O3, SO2, CO, HCHO, and PM1 are good. Pollution peaks around 9:00 AM (PM10: 49.5/100).
Tomorrow (21 September 2026): Air quality in Pasadena, California is fair. AQI improves to fair; PM2.5 decreases 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 AM (PM10: 31.6/100). Airmine updates local air quality forecasts four times daily.
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Pasadena's air quality reflects the San Gabriel Valley's enclosed position between the San Gabriel Mountains to the north and the Los Angeles basin to the south, sharing the region's notorious temperature inversion problem. Vehicle emissions from I-210 and SR-134 generate elevated NOₓ, while the Rose Bowl's event traffic contributes periodic peaks and the valley position means Pasadena accumulates some of the San Gabriel Valley's higher ozone and PM2.5 readings.
Today - 20 September | Pollution peaks at 09:00
AQI:
Moderate
49.5/100
PM2.5 (fine particles):
Moderate
41.4/100
PM10 (coarse particles):
Moderate
49.5/100
NO2 (nitrogen dioxide):
Fair
25.6/100
O3 (ozone):
Good
17.6/100
SO2 (sulfur dioxide):
Good
0.4/100
CO (carbon monoxide):
Good
0.4/100
HCHO (formaldehyde):
Good
1.1/100
PM1 (ultrafine particles):
Good
4.4/100
Levels show the poorest local air quality during the day
Tomorrow - 21 September | Pollution peaks at 00:00
AQI:
Fair
31.6/100
PM2.5 (fine particles):
Fair
28.9/100
PM10 (coarse particles):
Fair
31.6/100
NO2 (nitrogen dioxide):
Good
11.8/100
O3 (ozone):
Fair
22.5/100
SO2 (sulfur dioxide):
Good
0.6/100
CO (carbon monoxide):
Good
0.5/100
HCHO (formaldehyde):
Good
1.9/100
PM1 (ultrafine particles):
Good
6.1/100
Pollen forecast in Pasadena, California
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Frequently Asked Questions
Is air quality bad in Pasadena, California right now?
On 20 September 2026, overall air quality in Pasadena, California is moderate. AQI is the main air quality indicator at 49.5/100. Pollution peaks around 9:00 AM (PM10: 49.5/100).
Will air quality be worse tomorrow in Pasadena, California?
On 21 September 2026, air quality conditions in Pasadena, California will be better than today, with AQI forecast at fair at 31.6/100. Pollution peaks around 12:00 AM (PM10: 31.6/100).
When is air pollution at its worst in Pasadena, California?
Pasadena's air quality has a clear seasonal rhythm, as winter rains provide the only real relief from an otherwise persistent haze; by contrast, 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 Pasadena, California 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 20:27 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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