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.

Ranked by unhealthy days: the share of each city's measured days with a daily mean over 35.4 µg/m³ (US AQI 101+), Unhealthy for Sensitive Groups or worse on the US EPA's scale. Ties go to the higher average.

Gunma: 8 measured citiesIshikawa: 9 measured citiesKanagawa: 21 measured citiesNagano: 12 measured citiesNiigata: 12 measured citiesSaitama: 31 measured citiesShizuoka: 19 measured citiesTokyo: 10 measured citiesToyamaYamanashi: 7 measured citiesAichi: 23 measured citiesGifu: 15 measured cities#11 Saku: 3.0 µg/m³#12 Hakuba: 3.0 µg/m³#10 Ina: 3.1 µg/m³#9 Ueda: 3.3 µg/m³#8 Okaya: 3.4 µg/m³#7 Kiso: 3.8 µg/m³#6 Chikuma: 3.9 µg/m³#4 Obuse: 4.3 µg/m³#5 Matsumoto: 4.3 µg/m³#3 Suwa: 4.4 µg/m³#2 Nagano: 4.5 µg/m³#1 Iida: 5.0 µg/m³
Each dot is a measured city, coloured by its PM2.5; tap a dot to open the city.
← Iida 0% 0.75%0
Every measured city in Nagano, Japan, one column each, ranked by unhealthy days: height is the share of its measured days that were unhealthy, colour its average. Point at it to read a city; tap to open it.
  1. 1Iida 0%
  2. 2Nagano 0%
  3. 3Suwa 0%
  4. 4Obuselast full day 2 Oct 0%
  5. 4Matsumoto 0%
  6. 6Chikuma 0%
  7. 7Kisolast full day 3 Oct 0%
  8. 8Okaya 0%
  9. 9Ueda 0%
  10. 10Ina 0%
  11. 11Saku 0%
  12. 11Hakubalast full day 3 Oct 0%
Good0–50
Moderate51–100
Sensitive groups101–150
Unhealthy151–200
Very unhealthy201–300
Hazardous301+

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.

City7-day estimateBand
Azumino≈ 5 µg/m³Good
Shiojiri≈ 5 µg/m³Good
Chino≈ 5 µg/m³Good
Suzaka≈ 6 µg/m³Good
Komoro≈ 5 µg/m³Good
Nakano≈ 6 µg/m³Good
Hotaka≈ 5 µg/m³Good
Komagane≈ 5 µg/m³Good
Tōmi≈ 5 µg/m³Good
Toyoshina≈ 5 µg/m³Good
Ōmachi≈ 5 µg/m³Good
Kamimaruko≈ 5 µg/m³Good
Kinoshita≈ 6 µg/m³Good
Iiyama≈ 6 µg/m³Good
Shimosuwa≈ 5 µg/m³Good
Karuizawa≈ 5 µg/m³Good
Tatsuno≈ 5 µg/m³Good
Minamiminowa≈ 6 µg/m³Good
Miyota≈ 5 µg/m³Good
Sakaki≈ 5 µg/m³Good

Bad-air episodes in Nagano

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.

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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.