Portsmouth Air Quality Forecast - Today, Tomorrow
Air Quality Today
Today (16 October): Air quality in Portsmouth is good. AQI, PM2.5, PM10, NO2, O3, SO2, CO, HCHO, and PM1 are good. Pollution peaks around 12:00 PM (NO2: 25.3/100).
Air Quality Tomorrow
Tomorrow (17 October 2026): Air quality in Portsmouth is good. All pollutants stay as today. Pollution peaks around 10:00 PM (PM10: 21.7/100).
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Air Quality
Today - 16 October
| Pollutant | Level | Value |
|---|---|---|
| AQI | Good | 16.2/100 |
| PM2.5 (fine particles) | Good | 6.3/100 |
| PM10 (coarse particles) | Good | 7.3/100 |
| NO2 (nitrogen dioxide) | Good | 11.8/100 |
| O3 (ozone) | Good | 13.9/100 |
| SO2 (sulfur dioxide) | Good | 1.2/100 |
| CO (carbon monoxide) | Good | 0.5/100 |
| HCHO (formaldehyde) | Good | 1.5/100 |
| PM1 (ultrafine particles) | Good | 6.0/100 |
Tomorrow - 17 October
| Pollutant | Level | Value |
|---|---|---|
| AQI | Good | 14.8/100 |
| PM2.5 (fine particles) | Good | 7.8/100 |
| PM10 (coarse particles) | Good | 9.4/100 |
| NO2 (nitrogen dioxide) | Good | 9.2/100 |
| O3 (ozone) | Good | 12.9/100 |
| SO2 (sulfur dioxide) | Good | 1.3/100 |
| CO (carbon monoxide) | Good | 0.5/100 |
| HCHO (formaldehyde) | Good | 2.3/100 |
| PM1 (ultrafine particles) | Good | 6.4/100 |
Local Environmental Conditions
Around the center of Portsmouth, dense development means road traffic is the main local source of nitrogen dioxide and fine particles. Home heating, especially wood stoves and fireplaces, adds smoke and fine particles in the colder months. Winds here are fairly strong, averaging around 20 km/h, which helps disperse local pollution. Pollution carried in from the wider region can also raise levels at times.
Ozone rises a little on sunny days from June to September, but the mild summers, around 19°C, keep it in check. In contrast, particle levels tend to be highest from December to March, when home heating and traffic add more emissions and cold, calm spells at around 6°C can leave a light winter haze over the city.
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Frequently Asked Questions About Air Quality in Portsmouth
Is air quality bad in Portsmouth right now?
On 16 October 2026, overall air quality in Portsmouth is good. AQI is the main air quality indicator at 16.2/100. Pollution peaks around 12:00 PM (NO2: 25.3/100).
Will air quality be worse tomorrow in Portsmouth?
On 17 October 2026, air quality conditions in Portsmouth will be similar to today, with AQI forecast at good at 14.8/100. Pollution peaks around 10:00 PM (PM10: 21.7/100).
When is air pollution at its worst in Portsmouth?
Ozone rises a little on sunny days from June to September, but the mild summers, around 19°C, keep it in check. In contrast, particle levels tend to be highest from December to March, when home heating and traffic add more emissions and cold, calm spells at around 6°C can leave a light winter haze over the city.
Are air quality levels in Portsmouth 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. |