Air quality
Air quality in Sejong 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, 3:00 am (18:00 UTC).
Live AQI, PM2.5, PM10 and ozone for Sejong, Sejong-si, South Korea, with a 48-hour forecast and the best time to be outside.
- US AQI now
- 56 Moderate
- PM2.5
- 12 µg/m³ 0.8× WHO 24-h guideline
- PM10
- 15 µg/m³
- Ozone
- 70 µg/m³
- Dominant pollutant
- PM2.5 sub-index 56
- Best hour today
- 11:00 am AQI 53
- European AQI
- 33
Air quality in Sejong right now
Right now the modelled US Air Quality Index for Sejong, Sejong-si, South Korea 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 12 µg/m³, within the WHO 24-hour guideline of 15 µg/m³; PM10 is 15 µg/m³ against a guideline of 45; ozone is 70 µg/m³ (below the WHO 8-hour level of 100); nitrogen dioxide is 4.8 µg/m³ (below the 24-hour guideline of 25).
Also this hour: carbon monoxide 139 µg/m³.
NASA FIRMS shows 2 fire hotspots within 300 km in the last day (nearest about 171 km), but particle levels are not elevated enough to point to smoke right now.
Sejong AQI forecast: next 48 hours
Over the next 24 hours the AQI is forecast to range from 53 around Mon 11:00 am to 61 around Tue 12:00 am, staying "Moderate" throughout.
The following day looks similar, averaging about 56.
| Local time (Asia/Seoul) | US AQI | Category | PM2.5 µg/m³ | PM10 µg/m³ | Ozone µg/m³ |
|---|---|---|---|---|---|
| Mon 3:00 am | 56 | Moderate | 11.5 | 15 | 70 |
| Mon 6:00 am | 55 | Moderate | 13.2 | 18 | 65 |
| Mon 9:00 am | 54 | Moderate | 15.4 | 20 | 58 |
| Mon 12:00 pm | 53 | Moderate | 16.3 | 22 | 78 |
| Mon 3:00 pm | 54 | Moderate | 15.5 | 21 | 76 |
| Mon 6:00 pm | 56 | Moderate | 18.2 | 23 | 6 |
| Mon 9:00 pm | 59 | Moderate | 16.2 | 20 | 3 |
| Tue 12:00 am | 61 | Moderate | 14.2 | 18 | 15 |
| Tue 3:00 am | 61 | Moderate | 8.8 | 11 | 55 |
| Tue 6:00 am | 61 | Moderate | 10 | 13 | 46 |
| Tue 9:00 am | 60 | Moderate | 9 | 11 | 43 |
| Tue 12:00 pm | 58 | Moderate | 9.5 | 16 | 66 |
| Tue 3:00 pm | 57 | Moderate | 11 | 17 | 76 |
| Tue 6:00 pm | 55 | Moderate | 5.9 | 7 | 59 |
| Tue 9:00 pm | 52 | Moderate | 5.2 | 6 | 57 |
| Wed 12:00 am | 49 | Good | 6.3 | 7 | 47 |
| Wed 3:00 am | 45 | Good | 6.5 | 8 | 43 |
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 Sejong today
Between 6 am and 9 pm local time, the cleanest air today is forecast around 11:00 am (AQI 53, Moderate) and the worst around 9:00 pm (AQI 59). The difference across the day is small, so timing matters little.
Sejong vs the rest of South Korea
Across 42 South Korea cities we track, the average US AQI right now is 55 (Moderate). Sejong at 56 is about average.
It ranks 21 of 42 from cleanest to most polluted; the cleanest is Chinju (24) and the most polluted Ansan-si (75).
For context, the median across 3,909 cities worldwide is 57.
Air quality in cities near Sejong
| City | Distance | US AQI | Category | PM2.5 µg/m³ |
|---|---|---|---|---|
| Cheongju-si | 18 km | 53 | Moderate | 12.3 |
| Cheonan | 27 km | 65 | Moderate | 11.9 |
| Daejeon | 28 km | 56 | Moderate | 11.5 |
| Pyeongtaek | 48 km | 65 | Moderate | 11.9 |
| Osan | 65 km | 73 | Moderate | 12.2 |
| Iksan | 78 km | 52 | Moderate | 8.1 |
| Suwon | 80 km | 73 | Moderate | 12.2 |
| Hwaseong-si | 80 km | 75 | Moderate | 14.6 |
Model vs measured
We found no measured PM2.5 sensor cell within 25 km of Sejong, 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 Sejong
Air quality elsewhere
Data: Open-Meteo Air Quality API, Copernicus Atmosphere Monitoring Service (CAMS), NASA FIRMS.