Air quality
Air quality in Semnan today
Updated
Moderate (US AQI 56) Acceptable for most people. Unusually sensitive people should consider shortening long or heavy exertion outdoors. Model estimate for Mon, Oct 26, 5:30 am (02:00 UTC).
Live AQI, PM2.5, PM10 and ozone for Semnan, Iran, with a 48-hour forecast and the best time to be outside.
- US AQI now
- 56 Moderate
- PM2.5
- 5.9 µg/m³ 0.4× WHO 24-h guideline
- PM10
- 8.5 µg/m³
- Ozone
- 39 µg/m³
- Dominant pollutant
- PM2.5 sub-index 56
- Best hour today
- 4:30 pm AQI 53
- European AQI
- 22
Air quality in Semnan right now
Right now the modelled US Air Quality Index for Semnan, Iran is 56, which falls in the "Moderate" band (up to 100). Acceptable for most people. Unusually sensitive people should consider shortening long or heavy exertion outdoors.
The index is driven mainly by PM2.5, whose own sub-index is 56. Fine and coarse particles come from traffic, heating, industry, dust and smoke; they build up on calm nights and clear when wind or rain arrives.
PM2.5 is 5.9 µg/m³, within the WHO 24-hour guideline of 15 µg/m³; PM10 is 8.5 µg/m³ against a guideline of 45; ozone is 39 µg/m³ (below the WHO 8-hour level of 100); nitrogen dioxide is 10 µg/m³ (below the 24-hour guideline of 25).
Also this hour: carbon monoxide 239 µg/m³.
NASA FIRMS shows 11 fire hotspots within 300 km in the last day (nearest about 118 km), but particle levels are not elevated enough to point to smoke right now.
Semnan AQI forecast: next 48 hours
Over the next 24 hours the AQI is forecast to range from 53 around Mon 4:30 pm to 61 around Tue 5:30 am, staying "Moderate" throughout.
The following day is expected to be worse, averaging about 64 against 56 for the next 24 hours.
| Local time (Asia/Tehran) | US AQI | Category | PM2.5 µg/m³ | PM10 µg/m³ | Ozone µg/m³ |
|---|---|---|---|---|---|
| Mon 5:30 am | 56 | Moderate | 5.9 | 9 | 39 |
| Mon 8:30 am | 55 | Moderate | 9.9 | 19 | 83 |
| Mon 11:30 am | 55 | Moderate | 10.8 | 24 | 112 |
| Mon 2:30 pm | 54 | Moderate | 8.1 | 18 | 113 |
| Mon 5:30 pm | 54 | Moderate | 12.9 | 26 | 105 |
| Mon 8:30 pm | 55 | Moderate | 30 | 51 | 80 |
| Mon 11:30 pm | 57 | Moderate | 20 | 26 | 39 |
| Tue 2:30 am | 59 | Moderate | 15.8 | 20 | 23 |
| Tue 5:30 am | 61 | Moderate | 14.3 | 18 | 13 |
| Tue 8:30 am | 63 | Moderate | 12.7 | 23 | 74 |
| Tue 11:30 am | 63 | Moderate | 14 | 35 | 116 |
| Tue 2:30 pm | 65 | Moderate | 15.3 | 38 | 122 |
| Tue 5:30 pm | 67 | Moderate | 18.3 | 39 | 108 |
| Tue 8:30 pm | 66 | Moderate | 18.7 | 31 | 74 |
| Tue 11:30 pm | 64 | Moderate | 15.2 | 20 | 47 |
| Wed 2:30 am | 63 | Moderate | 12.5 | 15 | 41 |
| Wed 5:30 am | 62 | Moderate | 14.5 | 19 | 44 |
Every third hour of the CAMS forecast via Open-Meteo. US AQI uses rolling averages (24 h for particles, 8 h for ozone), so it moves more slowly than the hourly concentrations.
Best time to be outside in Semnan today
Between 6 am and 9 pm local time, the cleanest air today is forecast around 4:30 pm (AQI 53, Moderate) and the worst around 6:30 am (AQI 56). The difference across the day is small, so timing matters little.
Semnan vs the rest of Iran
Across 33 Iran cities we track, the average US AQI right now is 70 (Moderate). Semnan at 56 is 14 points cleaner than average.
For context, the median across 3,556 cities worldwide is 58.
Air quality in cities near Semnan
| City | Distance | US AQI | Category | PM2.5 µg/m³ |
|---|---|---|---|---|
| Tehran | 179 km | 93 | Moderate | 23.2 |
| Eslamshahr | 195 km | 130 | Unhealthy for Sensitive Groups | 45.2 |
| Golestān | 200 km | 130 | Unhealthy for Sensitive Groups | 45.2 |
| Nasimshahr | 202 km | 130 | Unhealthy for Sensitive Groups | 45.2 |
| Qods | 207 km | 75 | Moderate | 20.8 |
| Shahrīār | 211 km | 75 | Moderate | 20.8 |
| Shahre Jadide Andisheh | 215 km | 75 | Moderate | 20.8 |
| Fardīs | 217 km | 75 | Moderate | 20.8 |
Model vs measured
We found no measured PM2.5 sensor cell within 25 km of Semnan, so the numbers on this page are model estimates. Models capture regional pollution well but can miss very local sources such as a busy road or a nearby fire.
Advice for sensitive groups
At 56, most people are fine outdoors. If you are unusually sensitive to PM2.5, keep long or intense workouts to the cleaner hours shown above.
What the US AQI numbers mean
| US AQI | Category | What it means |
|---|---|---|
| 0-50 | Good | Air quality is satisfactory and poses little or no risk; a good time for outdoor activity. |
| 51-100 | Moderate | Acceptable for most people. Unusually sensitive people should consider shortening long or heavy exertion outdoors. |
| 101-150 | Unhealthy for Sensitive Groups | People with heart or lung disease, older adults, children and teens should cut back on prolonged or heavy exertion outdoors. |
| 151-200 | Unhealthy | Everyone should reduce prolonged or heavy exertion outdoors; sensitive groups should avoid it and keep windows closed. |
| 201-300 | Very Unhealthy | Health alert: everyone should avoid prolonged or heavy exertion outdoors, and sensitive groups should stay indoors. |
| 301-500 | Hazardous | Emergency conditions: everyone should avoid all outdoor physical activity and stay indoors with filtered air if possible. The scale tops out at 500; heavier dust or smoke is shown as 500. |
Values on this page are modelled by CAMS (Copernicus) and served by Open-Meteo; they are estimates for the area around the city centre, not readings from an official monitor.
Nearby cities
More for Semnan
Air quality elsewhere
Data: Open-Meteo Air Quality API, Copernicus Atmosphere Monitoring Service (CAMS), NASA FIRMS.