Worst air pollution Siena, today and tomorrow
Today (9 August): Air quality in Siena is fair. NO2 is fair; AQI and O3 are medium; PM2.5, PM10, SO2, CO, HCHO, and PM1 are good. Pollution peaks around 6:00 PM (O3: 53.6/100).
Tomorrow (10 August 2026): Air quality in Siena is poor. AQI worsens to poor; O3 increases to poor; all other pollutants stay as today. Pollution peaks around 4:00 PM (O3: 63.4/100). 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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Siena's air quality benefits from its elevated Tuscan hill position at 322 metres, with consistent Tuscan hillside breezes providing reliable ventilation across this UNESCO heritage medieval city. Vehicle traffic on the SR2 Cassia and tourism operations are the primary local sources, while the surrounding Crete Senesi and Chianti hills create topographic variation and Siena's medieval core with significant car restrictions and the elevated hilltop position generally maintain moderate to good conditions throughout most of the year.
Today - 9 August | Pollution peaks at 18:00
AQI:
Medium
53.6/100
PM2.5 (fine particles):
Good
10.4/100
PM10 (coarse particles):
Good
3.3/100
NO2 (nitrogen dioxide):
Fair
32.5/100
O3 (ozone):
Medium
53.6/100
SO2 (sulfur dioxide):
Good
4.9/100
CO (carbon monoxide):
Good
0.0/100
HCHO (formaldehyde):
Good
17.4/100
PM1 (ultrafine particles):
Good
12.6/100
Levels show the poorest local air quality during the day
Tomorrow - 10 August | Pollution peaks at 16:00
AQI:
Poor
63.4/100
PM2.5 (fine particles):
Good
16.5/100
PM10 (coarse particles):
Good
5.2/100
NO2 (nitrogen dioxide):
Fair
37.5/100
O3 (ozone):
Poor
63.4/100
SO2 (sulfur dioxide):
Good
7.7/100
CO (carbon monoxide):
Good
0.0/100
HCHO (formaldehyde):
Good
15.1/100
PM1 (ultrafine particles):
Good
18.9/100
Pollen forecast in Siena
View pollen forecastFrequently Asked Questions
Is air quality bad in Siena right now?
On 9 August 2026, overall air quality in Siena is fair. NO2 is the main pollutant at 32.5/100. Pollution peaks around 6:00 PM (O3: 53.6/100).
Will air quality be worse tomorrow in Siena?
On 10 August 2026, air quality conditions in Siena will be worse than today, with AQI forecast at poor at 63.4/100. Pollution peaks around 4:00 PM (O3: 63.4/100).
When is air pollution at its worst in Siena?
Siena residents notice reduced air quality mainly when below oak and linden pollen peaks, and during spells of significant car restrictions; otherwise, the area's setting generally supports clear, well-ventilated conditions.
Are air quality levels in Siena 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: 9 August 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.
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