Worst air pollution San Luis Obispo, today and tomorrow
Today (20 September): Air quality in San Luis Obispo is moderate. AQI, PM10, and NO2 are moderate; PM2.5, O3, and PM1 are fair; SO2, CO, and HCHO are good. Pollution peaks around 5:00 PM (NO2: 45.4/100).
Tomorrow (21 September 2026): Air quality in San Luis Obispo is moderate. PM10 decreases to fair; all other pollutants stay as today. Pollution peaks around 4:00 PM (NO2: 52.6/100). 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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San Luis Obispo's air quality is shaped largely by Central Coast marine air; afternoon sea breeze generally keeps conditions favorable. Overall, San Luis Obispo sees air quality that tracks fairly closely with typical conditions for its wider region. Visitors and residents alike tend to notice the clearest air outside the warmest summer weeks.
Today - 20 September | Pollution peaks at 17:00
AQI:
Moderate
45.4/100
PM2.5 (fine particles):
Fair
36.6/100
PM10 (coarse particles):
Moderate
42.1/100
NO2 (nitrogen dioxide):
Moderate
45.4/100
O3 (ozone):
Fair
23.6/100
SO2 (sulfur dioxide):
Good
2.2/100
CO (carbon monoxide):
Good
0.6/100
HCHO (formaldehyde):
Good
2.3/100
PM1 (ultrafine particles):
Fair
22.2/100
Levels show the poorest local air quality during the day
Tomorrow - 21 September | Pollution peaks at 16:00
AQI:
Moderate
52.6/100
PM2.5 (fine particles):
Fair
31.1/100
PM10 (coarse particles):
Fair
22.6/100
NO2 (nitrogen dioxide):
Moderate
52.6/100
O3 (ozone):
Fair
34.9/100
SO2 (sulfur dioxide):
Good
1.7/100
CO (carbon monoxide):
Good
0.6/100
HCHO (formaldehyde):
Good
2.4/100
PM1 (ultrafine particles):
Fair
21.3/100
Pollen forecast in San Luis Obispo
View pollen forecastAir quality forecasts for neighbourhoods and landmarks in San Luis Obispo
Frequently Asked Questions
Is air quality bad in San Luis Obispo right now?
On 20 September 2026, overall air quality in San Luis Obispo is moderate. AQI is the main air quality indicator at 45.4/100. Pollution peaks around 5:00 PM (NO2: 45.4/100).
Will air quality be worse tomorrow in San Luis Obispo?
On 21 September 2026, air quality conditions in San Luis Obispo will be similar to today, with AQI forecast at moderate at 52.6/100. Pollution peaks around 4:00 PM (NO2: 52.6/100).
When is air pollution at its worst in San Luis Obispo?
San Luis Obispo's air quality has a clear seasonal rhythm — the shortest stretch of clean air usually falls in the wetter winter months, whereas from August into October, wildfire smoke can add sharp particulate spikes on top of the usual summer ozone. Coastal breezes offer some relief compared to inland valley locations that see heavier smog buildup.
Are air quality levels in San Luis Obispo 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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