Worst air pollution Viana do Castelo, today and tomorrow
Today (20 September): Air quality in Viana do Castelo is good. AQI, PM2.5, PM10, NO2, O3, SO2, CO, HCHO, and PM1 are good. Pollution peaks around 4:00 PM (O3: 19.3/100).
Tomorrow (21 September 2026): Air quality in Viana do Castelo is fair. AQI worsens to fair; NO2 increases to fair; O3 increases to fair; PM1 increases to fair; all other pollutants stay as today. Pollution peaks around 7:00 AM (NO2: 26.5/100). 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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Viana do Castelo's air quality benefits from its exceptional Atlantic and Lima river estuary position in the Minho region, with consistent Atlantic westerlies and the river estuary providing reliable maritime ventilation. Vehicle traffic on the A28 and surrounding industrial and port operations are the primary local sources, while the outstanding Atlantic coastal proximity and the Lima valley's ventilation corridor generally maintain Viana do Castelo among Portugal's cleaner northern urban environments.
Today - 20 September | Pollution peaks at 16:00
AQI:
Good
19.3/100
PM2.5 (fine particles):
Good
12.2/100
PM10 (coarse particles):
Good
11.8/100
NO2 (nitrogen dioxide):
Good
17.6/100
O3 (ozone):
Good
19.3/100
SO2 (sulfur dioxide):
Good
0.9/100
CO (carbon monoxide):
Good
0.6/100
HCHO (formaldehyde):
Good
3.2/100
PM1 (ultrafine particles):
Good
15.6/100
Levels show the poorest local air quality during the day
Tomorrow - 21 September | Pollution peaks at 07:00
AQI:
Fair
26.5/100
PM2.5 (fine particles):
Good
14.1/100
PM10 (coarse particles):
Good
11.5/100
NO2 (nitrogen dioxide):
Fair
26.5/100
O3 (ozone):
Fair
21.6/100
SO2 (sulfur dioxide):
Good
0.8/100
CO (carbon monoxide):
Good
0.6/100
HCHO (formaldehyde):
Good
6.7/100
PM1 (ultrafine particles):
Fair
22.9/100
Pollen forecast in Viana do Castelo
View pollen forecastFrequently Asked Questions
Is air quality bad in Viana do Castelo right now?
On 20 September 2026, overall air quality in Viana do Castelo is good. AQI is the main air quality indicator at 19.3/100. Pollution peaks around 4:00 PM (O3: 19.3/100).
Will air quality be worse tomorrow in Viana do Castelo?
On 21 September 2026, air quality conditions in Viana do Castelo will be worse than today, with AQI forecast at fair at 26.5/100. Pollution peaks around 7:00 AM (NO2: 26.5/100).
When is air pollution at its worst in Viana do Castelo?
People in Viana do Castelo tend to notice reduced air quality when oak and eucalyptus pollen peaks, or because of vehicle traffic on the A28 and neighbouring industrial and port operations; outside of those periods, conditions here remain among the more favourable in the region.
Are air quality levels in Viana do Castelo 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 14:33 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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