San Diego Air Quality Forecast - Today, Tomorrow
Air Quality Today
Today (10 October): Air quality in San Diego is fair. AQI, PM2.5, and PM10 are fair; NO2, O3, SO2, CO, HCHO, and PM1 are good. Pollution peaks around 10:00 AM (PM10: 39.9/100).
Air Quality Tomorrow
Tomorrow (11 October 2026): Air quality in San Diego is fair. PM2.5 decreases to good; all other pollutants stay as today. Pollution peaks around 5:00 AM (PM10: 24.0/100).
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Air Quality
Today - 10 October
| Pollutant | Level | Value |
|---|---|---|
| AQI | Fair | 39.9/100 |
| PM2.5 (fine particles) | Fair | 22.9/100 |
| PM10 (coarse particles) | Fair | 39.9/100 |
| NO2 (nitrogen dioxide) | Good | 2.3/100 |
| O3 (ozone) | Good | 15.0/100 |
| SO2 (sulfur dioxide) | Good | 0.9/100 |
| CO (carbon monoxide) | Good | 0.4/100 |
| HCHO (formaldehyde) | Good | 1.3/100 |
| PM1 (ultrafine particles) | Good | 3.2/100 |
Tomorrow - 11 October
| Pollutant | Level | Value |
|---|---|---|
| AQI | Fair | 24.0/100 |
| PM2.5 (fine particles) | Good | 17.7/100 |
| PM10 (coarse particles) | Fair | 24.0/100 |
| NO2 (nitrogen dioxide) | Good | 4.1/100 |
| O3 (ozone) | Good | 12.8/100 |
| SO2 (sulfur dioxide) | Good | 0.5/100 |
| CO (carbon monoxide) | Good | 0.4/100 |
| HCHO (formaldehyde) | Good | 1.0/100 |
| PM1 (ultrafine particles) | Good | 3.2/100 |
Local Environmental Conditions
Air pollution in San Diego comes mainly from traffic, the port and sources across the border. Vehicles on I-5, I-15 and I-805 are the largest local source, while ships, the Navy bases and the Port of San Diego add diesel emissions along the bay. The marine layer often holds pollution close to the ground, and inland valleys such as El Cajon and Escondido see the most ozone. Traffic at the border crossings and emissions from Tijuana also affect air quality in South Bay.
San Diego's air quality follows the coastal seasons. From June to September, warm, sunny days drive ozone formation, especially in the inland valleys, while the marine layer can hold pollution near the coast. Wildfire season peaks from September to December, when hot, dry Santa Ana winds can fan fires in the backcountry and spread smoke and haze across the city, as during the Cedar Fire in 2003. Winter storms, when January averages around 14°C, usually bring the cleanest air in San Diego.
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Frequently Asked Questions About Air Quality in California
Is air quality bad in San Diego right now?
On 10 October 2026, overall air quality in San Diego is fair. AQI is the main air quality indicator at 39.9/100. Pollution peaks around 10:00 AM (PM10: 39.9/100).
Will air quality be worse tomorrow in San Diego?
On 11 October 2026, air quality conditions in San Diego will be similar to today, with AQI forecast at fair at 24.0/100. Pollution peaks around 5:00 AM (PM10: 24.0/100).
When is air pollution at its worst in San Diego?
San Diego's air quality follows the coastal seasons. From June to September, warm, sunny days drive ozone formation, especially in the inland valleys, while the marine layer can hold pollution near the coast. Wildfire season peaks from September to December, when hot, dry Santa Ana winds can fan fires in the backcountry and spread smoke and haze across the city, as during the Cedar Fire in 2003. Winter storms, when January averages around 14°C, usually bring the cleanest air in San Diego.
Are air quality levels in San Diego 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.
Understanding the Scale
The 0–100 air quality scores represent risk levels, not direct air pollutant concentrations. Higher scores indicate higher risk.
Air Quality
| Good | 0-20 | Low air quality risk. Air quality is expected to be good, with low levels of pollution. |
| Fair | 20-40 | Generally low air quality risk. Air quality is expected to be acceptable, with some pollution present. |
| Moderate | 40-60 | Moderate air quality risk. Air pollution is elevated and air quality may be less favorable. |
| Poor | 60-80 | High air quality risk. Air pollution is high and air quality is expected to be poor. |
| Very Poor | 80-100 | Very high air quality risk. Air pollution is very high and air quality is expected to be very poor. |