Worst air pollution Seixal, today and tomorrow

Today (21 July): Air quality in Seixal is medium. AQI and O3 are medium; PM2.5, PM10, NO2, SO2, CO, HCHO, and PM1 are good. Pollution peaks around 3:00 PM (O3: 42.7/100).
Tomorrow (22 July 2026): Air quality in Seixal is fair. AQI worsens to fair; O3 increases to fair; all other pollutants stay as today. Pollution peaks around 12:00 PM (O3: 33.7/100). Airmine updates local air quality forecasts four times daily.

For long term forecasts and maps, see the Airmine app

Developed with support from the European Space Agency (ESA)’s Business Applications and Space Solutions (BASS) team

Use our Strava plugin to check your own exposure.

Seixal's air quality reflects its position on the southern bank of the Tagus estuary opposite Lisbon, with the Seixal industrial zone's steel and chemical operations and heavy traffic on the A2 contributing elevated PM2.5 and SO₂. The Tagus estuary generally provides ventilation from Atlantic westerlies, while the Arrábida Natural Park to the south provides a clean-air backdrop, and the prevailing northwesterly winds over the estuary generally carry Lisbon's urban emissions southward toward the Seixal and Almada shoreline.

Today - 21 July | Pollution peaks at 15:00

AQI:

Medium

42.7/100

PM2.5 (fine particles):

Good

12.6/100

PM10 (coarse particles):

Good

9.7/100

NO2 (nitrogen dioxide):

Good

0.6/100

O3 (ozone):

Medium

42.7/100

SO2 (sulfur dioxide):

Good

0.1/100

CO (carbon monoxide):

Good

0.0/100

HCHO (formaldehyde):

Good

9.3/100

PM1 (ultrafine particles):

Good

8.5/100

Levels show the poorest local air quality during the day

Tomorrow - 22 July | Pollution peaks at 12:00

AQI:

Fair

33.7/100

PM2.5 (fine particles):

Good

13.0/100

PM10 (coarse particles):

Good

10.8/100

NO2 (nitrogen dioxide):

Good

0.3/100

O3 (ozone):

Fair

33.7/100

SO2 (sulfur dioxide):

Good

0.1/100

CO (carbon monoxide):

Good

0.0/100

HCHO (formaldehyde):

Good

3.2/100

PM1 (ultrafine particles):

Good

8.5/100

Pollen forecast in Seixal

View pollen forecast

Frequently Asked Questions

Is air quality bad in Seixal right now?

On 21 July 2026, overall air quality in Seixal is medium. AQI is the main air quality indicator at 42.7/100. Pollution peaks around 3:00 PM (O3: 42.7/100).

Will air quality be worse tomorrow in Seixal?

On 22 July 2026, air quality conditions in Seixal will be worse than today, with AQI forecast at fair at 33.7/100. Pollution peaks around 12:00 PM (O3: 33.7/100).

When is air pollution at its worst in Seixal?

People in Seixal tend to notice reduced air quality when estuary pine and eucalyptus pollen peaks, or because of the Seixal industrial zone's steel and chemical operations and heavy traffic on the A2; conditions usually ease once the wet season or windier weather returns.

Are air quality levels in Seixal 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.

Want to see air quality forecasts for other cities in Portugal?

Check air quality in other popular cities:

Data provided by Airmine — Last update: 21 July 2026 at 10:44 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.

For long term forecasts and maps, see the Airmine app