Worst air pollution Diamond Bar, today and tomorrow
Today (9 August): Air quality in Diamond Bar is fair. AQI, PM2.5, PM10, and O3 are fair; NO2, SO2, CO, HCHO, and PM1 are good. Pollution peaks around 6:00 PM (PM10: 28.3/100).
Tomorrow (10 August 2026): Air quality in Diamond Bar is fair. PM2.5 decreases to good; PM10 decreases to good; all other pollutants stay as today. Pollution peaks around 10:00 AM (O3: 23.8/100). 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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Diamond Bar's air quality reflects the Pomona Valley's enclosed position in the eastern Los Angeles basin, with vehicle emissions from SR-57 and SR-60 the primary local sources. The basin inversion affects all of the eastern Los Angeles-San Gabriel Valley corridor, while Diamond Bar's hillside position provides marginally better topographic variation than the flat valley floor, though the persistent basin inversion continues to concentrate ozone and PM2.5 and the valley position tracks at consistently elevated suburban readings throughout the year.
Today - 9 August | Pollution peaks at 18:00
AQI:
Fair
28.3/100
PM2.5 (fine particles):
Fair
20.5/100
PM10 (coarse particles):
Fair
28.3/100
NO2 (nitrogen dioxide):
Good
0.5/100
O3 (ozone):
Fair
24.1/100
SO2 (sulfur dioxide):
Good
0.9/100
CO (carbon monoxide):
Good
0.0/100
HCHO (formaldehyde):
Good
1.4/100
PM1 (ultrafine particles):
Good
5.7/100
Levels show the poorest local air quality during the day
Tomorrow - 10 August | Pollution peaks at 10:00
AQI:
Fair
23.8/100
PM2.5 (fine particles):
Good
13.1/100
PM10 (coarse particles):
Good
14.0/100
NO2 (nitrogen dioxide):
Good
1.1/100
O3 (ozone):
Fair
23.8/100
SO2 (sulfur dioxide):
Good
1.0/100
CO (carbon monoxide):
Good
0.0/100
HCHO (formaldehyde):
Good
2.4/100
PM1 (ultrafine particles):
Good
5.8/100
Pollen forecast in Diamond Bar
View pollen forecastFrequently Asked Questions
Is air quality bad in Diamond Bar right now?
On 9 August 2026, overall air quality in Diamond Bar is fair. AQI is the main air quality indicator at 28.3/100. Pollution peaks around 6:00 PM (PM10: 28.3/100).
Will air quality be worse tomorrow in Diamond Bar?
On 10 August 2026, air quality conditions in Diamond Bar will be similar to today, with AQI forecast at fair at 23.8/100. Pollution peaks around 10:00 AM (O3: 23.8/100).
When is air pollution at its worst in Diamond Bar?
Diamond Bar experiences a distinct seasonal swing in air quality — winter typically brings the cleanest stretch, once occasional rain clears the basin, whereas summer sunshine and heat drive some of the worst ozone readings in the country. Coastal breezes offer some relief compared to inland valley locations that see heavier smog buildup.
Are air quality levels in Diamond Bar 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: 10 August 2026 at 02:34 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.
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