SmogRank / World / The Netherlands / North Holland / December 2025

Most unhealthy days in North Holland, The Netherlands, December 2025

8 cities in North Holland, The Netherlands ranked by their share of unhealthy days over the 31 days. The most unhealthy days: Haarlem, The Netherlands, 2 of 31 measured days. A city needs measurements on 70% of the days to be ranked.

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.

← Haarlem 6% 6%0
Every city in North Holland, The Netherlands ranked for December 2025, 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. 1Haarlemlow-cost sensors
    2 of 31
  2. 2Badhoevedorp
    0 of 29
  3. 3Zwanenburg
    0 of 29
  4. 3Velsen-Zuid
    0 of 29
  5. 5Amsterdam
    0 of 29
  6. 6Medemblik
    0 of 31
  7. 7Zaanstad
    0 of 29
  8. 8Wormer
    0 of 29

Low-cost sensors: consumer units, counted only in cities with no government-grade monitor; they read close to reference monitors on the whole, but 15 to 25% high in humid air. How we use them.

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

All cities in the world, December 2025 · All cities in The Netherlands, December 2025 · North Holland now

Use this board

SmogRank, most polluted cities in North Holland, The Netherlands, by unhealthy days, PM2.5, December 2025, smogrank.com/nl/region/north-holland/history/2025-12?by=days (accessed 7 Oct 2026).

Download top 10 by average (PNG)

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.