Worst air pollution Cardiff Bay - Caerdydd, today and tomorrow
Today (20 September): Air quality in Cardiff Bay is moderate. AQI and PM2.5 are moderate; PM10 and NO2 are fair; O3, SO2, CO, HCHO, and PM1 are good. Pollution peaks around 11:00 PM (PM2.5: 40.2/100).
Tomorrow (21 September 2026): Air quality in Cardiff Bay is moderate. NO2 increases to moderate; PM1 increases to fair; all other pollutants stay as today. Pollution peaks around 8:00 PM (NO2: 50.9/100). 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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The A40 generates consistent traffic-related NO₂ and PM2.5, particularly during peak commuting hours. Air quality in Cardiff Bay is shaped by its location in Cardiff, where vehicle traffic and everyday urban activity dominate local sources. Prevailing westerlies tend to disperse pollutants reasonably well, keeping readings close to typical UK small-town levels.
Today - 20 September | Pollution peaks at 23:00
AQI:
Moderate
40.2/100
PM2.5 (fine particles):
Moderate
40.2/100
PM10 (coarse particles):
Fair
23.8/100
NO2 (nitrogen dioxide):
Fair
30.8/100
O3 (ozone):
Good
12.7/100
SO2 (sulfur dioxide):
Good
5.6/100
CO (carbon monoxide):
Good
0.9/100
HCHO (formaldehyde):
Good
8.3/100
PM1 (ultrafine particles):
Good
18.2/100
Levels show the poorest local air quality during the day
Tomorrow - 21 September | Pollution peaks at 20:00
AQI:
Moderate
50.9/100
PM2.5 (fine particles):
Moderate
47.9/100
PM10 (coarse particles):
Fair
38.7/100
NO2 (nitrogen dioxide):
Moderate
50.9/100
O3 (ozone):
Good
13.2/100
SO2 (sulfur dioxide):
Good
10.9/100
CO (carbon monoxide):
Good
1.3/100
HCHO (formaldehyde):
Good
15.7/100
PM1 (ultrafine particles):
Fair
32.8/100
Other Landmarks in Caerdydd
Frequently Asked Questions
Is air quality bad in Cardiff Bay right now?
On 20 September 2026, overall air quality in Cardiff Bay is moderate. AQI is the main air quality indicator at 40.2/100. Pollution peaks around 11:00 PM (PM2.5: 40.2/100).
Will air quality be worse tomorrow in Cardiff Bay?
On 21 September 2026, air quality conditions in Cardiff Bay will be similar to today, with AQI forecast at moderate at 50.9/100. Pollution peaks around 8:00 PM (NO2: 50.9/100).
When is air pollution at its worst in Cardiff Bay?
Ask a local in Cardiff Bay and they'll tell you air quality changes noticeably from season to season. Summer sunshine can drive up ozone locally, though overall air generally moves and clears more freely than in winter. The coldest months usually bring the worst readings, as heating and temperature inversions keep A40 emissions from dispersing normally. Spring and autumn tend to be the calmer, more moderate stretches by comparison.
Are air quality levels in Cardiff Bay 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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