SmogRank / World / Asia / Japan / Nagano
Most polluted cities in Nagano, Japan
12 measured cities, last 30 days; 0 above the WHO 24-hour guideline. Worst: Iida at 5.0 µg/m³, #2,260 in the world.
About 0 people in these 2 cities breathed unhealthy air on an average day over the last 30 days.
Ranked by people: each city's population times its share of unhealthy days, those with a daily mean over 35.4 µg/m³ (US AQI 101+). That is how many people living there breathed unhealthy air on an average day. Only cities measured at 2 or more places at least 3 km apart are ranked: one monitor shouldn't speak for a whole city. Population is the city itself, not its wider metro area.
The US EPA's Air Quality Index for PM2.5 (2024 breakpoints). Show values as: µg/m³ · US AQI · India AQI · China AQI · European AQI · UK DAQI · Canada AQHI+. About the scales
Estimated: cities without a monitor
Nagano cities we can't measure, with model estimates for the last 7 days. Listed by population, not ranked: estimates aren't precise enough to rank. Model estimates from the Copernicus Atmosphere Monitoring Service (CAMS), adjusted to measured cities nearby where there are any. Adjusted, a single day lands within ×1.5 of what a monitor would read about two times in three; unadjusted, it can be off by half or double. Treat them as a guide, not a measurement.
| City | 7-day estimate |
|---|---|
| Azumino | ≈ 5 µg/m³ |
| Shiojiri | ≈ 5 µg/m³ |
| Chino | ≈ 5 µg/m³ |
| Suzaka | ≈ 6 µg/m³ |
| Komoro | ≈ 5 µg/m³ |
| Nakano | ≈ 6 µg/m³ |
| Hotaka | ≈ 5 µg/m³ |
| Komagane | ≈ 5 µg/m³ |
| Tōmi | ≈ 5 µg/m³ |
| Toyoshina | ≈ 5 µg/m³ |
| Ōmachi | ≈ 5 µg/m³ |
| Kamimaruko | ≈ 5 µg/m³ |
| Kinoshita | ≈ 6 µg/m³ |
| Iiyama | ≈ 6 µg/m³ |
| Shimosuwa | ≈ 5 µg/m³ |
| Karuizawa | ≈ 5 µg/m³ |
| Tatsuno | ≈ 5 µg/m³ |
| Minamiminowa | ≈ 6 µg/m³ |
| Miyota | ≈ 5 µg/m³ |
| Sakaki | ≈ 5 µg/m³ |
Bad-air episodes in Nagano
- Japan and South Korea, July 202616 to 25 July 2026, 10 days205 cities39 µg/m³peak, Mooka
- Japan and South Korea, March 202623 to 31 March 2026, 9 days322 cities86 µg/m³peak, Pohang
- Japan, 4 to 5 August 20252 days130 cities44 µg/m³peak, Yamanashi
- Japan and South Korea, June and July 202530 June to 10 July 2025, 11 days532 cities117 µg/m³peak, Kōka
- Japan, May 202520 to 21 May 2025, 2 days107 cities34 µg/m³peak, Ayase
- Japan, 19 to 20 April 20252 days36 cities51 µg/m³peak, Hiratsuka
Times when many cities around here had PM2.5 at twice their usual or more on the same days.
Use this board
SmogRank, most polluted cities in Nagano, Japan, PM2.5, last 30 days to 6 Oct 2026, 22:00 UTC, smogrank.com/jp/region/nagano?w=30d.
You're welcome to reuse a single chart, image or figure with this citation and a link. Terms. Raw monitor readings in bulk are published by OpenAQ, under each provider's licence.
Updated 2026-10-06 22:07 UTC. Values are PM2.5 (fine particles), the median of each city's monitors, as the US AQI PM2.5 sub-index.