SmogRank / The Netherlands / North Holland

Air quality in Haarlem

North Holland, The Netherlands. PM2.5 from 3 low-cost sensors, updated hourly.

12.2 µg/m³
Moderate

Latest hour (04:00 UTC), 0.8× the WHO 24-hour guideline.

Rank

24 h
–
not enough data
7 days
#391
of 2,330 · 11.6 µg/m³
30 days
#1,948
of 2,327 · 4.6 µg/m³
Year
#439
of 2,160 · 11.6 µg/m³

Why it ranks here

Likely fire smoke. On Sep 27, when Haarlem averaged 17.3 µg/m³ (its typical day: 6.3), NASA satellites detected 81 fires within 300 km (16 within 100 km). Smoke from those fires is a likely contributor; we don't check which way the wind blew, and mapped smoke can be high above the ground.

Seasonal. Over the past year its worst months were January, February, averaging up to 28.6 µg/m³ against 4.3 in its cleanest month. Seasonal peaks usually come from heating, crop burning, fire or dust seasons.

Based on Haarlem's own measurements, with fire detections from NASA FIRMS and smoke maps from NOAA HMS; causes are the usual kinds for a pattern like this, not a confirmed source.

Last 4 days, hour by hour

15302026-10-01 00:00 UTC: 19.0 µg/m³2026-10-01 01:00 UTC: 21.3 µg/m³2026-10-01 02:00 UTC: 23.5 µg/m³2026-10-01 03:00 UTC: 22.5 µg/m³2026-10-01 04:00 UTC: 12.2 µg/m³Sep 28Sep 29Sep 30Oct 1

Times in UTC. Dashed line: WHO 24-hour guideline (15 µg/m³).

Every day for a year

SepNovDecJanFebMarAprMayJunJulAugSepMonWedFri2025-09-29: 15.6 µg/m³2025-09-30: 14.3 µg/m³2025-10-01: 28.0 µg/m³2025-10-02: 28.2 µg/m³2025-10-03: 17.6 µg/m³2025-10-04: 4.2 µg/m³2025-10-05: 1.3 µg/m³2025-10-06: 0.7 µg/m³2025-10-07: 6.5 µg/m³2025-10-08: 6.8 µg/m³2025-10-09: 1.0 µg/m³2025-10-10: 4.0 µg/m³2025-10-11: 10.4 µg/m³2025-10-12: 2.7 µg/m³2025-10-13: 1.5 µg/m³2025-10-14: 0.3 µg/m³2025-10-15: 0.1 µg/m³2025-10-16: 1.4 µg/m³2025-10-17: 0.6 µg/m³2025-10-18: 0.7 µg/m³2025-10-19: 10.9 µg/m³2025-10-20: 11.6 µg/m³2025-10-21: 1.8 µg/m³2025-10-22: 3.3 µg/m³2025-10-23: 3.1 µg/m³2025-10-24: 0.3 µg/m³2025-10-25: 0.2 µg/m³2025-10-26: 0.2 µg/m³2025-10-27: 0.4 µg/m³2025-10-28: 0.2 µg/m³2025-10-29: 7.8 µg/m³2025-10-30: 3.2 µg/m³2025-10-31: 5.5 µg/m³2025-11-01: 5.1 µg/m³2025-11-02: 1.9 µg/m³2025-11-03: 5.6 µg/m³2025-11-04: 0.6 µg/m³2025-11-05: 3.0 µg/m³2025-11-06: 12.5 µg/m³2025-11-07: 32.2 µg/m³2025-11-08: 37.1 µg/m³2025-11-09: 14.7 µg/m³2025-11-10: 19.3 µg/m³2025-11-11: 11.9 µg/m³2025-11-12: 6.4 µg/m³2025-11-13: 12.5 µg/m³2025-11-14: no data2025-11-15: 9.4 µg/m³2025-11-16: 13.8 µg/m³2025-11-17: 2.1 µg/m³2025-11-18: 1.1 µg/m³2025-11-19: 7.9 µg/m³2025-11-20: 8.3 µg/m³2025-11-21: 22.8 µg/m³2025-11-22: 27.9 µg/m³2025-11-23: 13.8 µg/m³2025-11-24: 16.0 µg/m³2025-11-25: 12.8 µg/m³2025-11-26: 31.6 µg/m³2025-11-27: 31.1 µg/m³2025-11-28: 19.9 µg/m³2025-11-29: 18.7 µg/m³2025-11-30: 0.4 µg/m³2025-12-01: 4.3 µg/m³2025-12-02: 5.0 µg/m³2025-12-03: 25.4 µg/m³2025-12-04: 22.2 µg/m³2025-12-05: 31.8 µg/m³2025-12-06: 5.6 µg/m³2025-12-07: 10.9 µg/m³2025-12-08: 1.0 µg/m³2025-12-09: 6.1 µg/m³2025-12-10: 3.1 µg/m³2025-12-11: 19.8 µg/m³2025-12-12: 29.4 µg/m³2025-12-13: 13.8 µg/m³2025-12-14: 34.9 µg/m³2025-12-15: 29.5 µg/m³2025-12-16: 24.7 µg/m³2025-12-17: 21.7 µg/m³2025-12-18: 9.4 µg/m³2025-12-19: 4.7 µg/m³2025-12-20: 31.7 µg/m³2025-12-21: 37.2 µg/m³2025-12-22: 38.5 µg/m³2025-12-23: 30.9 µg/m³2025-12-24: 9.7 µg/m³2025-12-25: 5.9 µg/m³2025-12-26: 32.4 µg/m³2025-12-27: 14.9 µg/m³2025-12-28: 15.9 µg/m³2025-12-29: 3.4 µg/m³2025-12-30: 3.6 µg/m³2025-12-31: 2.8 µg/m³2026-01-01: 6.5 µg/m³2026-01-02: 0.6 µg/m³2026-01-03: 0.4 µg/m³2026-01-04: 0.4 µg/m³2026-01-05: 4.0 µg/m³2026-01-06: 6.8 µg/m³2026-01-07: 27.7 µg/m³2026-01-08: 18.2 µg/m³2026-01-09: 26.0 µg/m³2026-01-10: 14.5 µg/m³2026-01-11: 30.5 µg/m³2026-01-12: 23.7 µg/m³2026-01-13: 21.6 µg/m³2026-01-14: 9.7 µg/m³2026-01-15: 17.0 µg/m³2026-01-16: 9.9 µg/m³2026-01-17: 36.3 µg/m³2026-01-18: 49.6 µg/m³2026-01-19: 47.3 µg/m³2026-01-20: 42.5 µg/m³2026-01-21: 30.0 µg/m³2026-01-22: 41.7 µg/m³2026-01-23: 49.2 µg/m³2026-01-24: 56.3 µg/m³2026-01-25: 68.3 µg/m³2026-01-26: 38.4 µg/m³2026-01-27: 28.6 µg/m³2026-01-28: 49.0 µg/m³2026-01-29: 47.6 µg/m³2026-01-30: 44.6 µg/m³2026-01-31: 39.6 µg/m³2026-02-01: 32.8 µg/m³2026-02-02: 51.1 µg/m³2026-02-03: 56.7 µg/m³2026-02-04: 39.7 µg/m³2026-02-05: 64.7 µg/m³2026-02-06: 51.8 µg/m³2026-02-07: 18.9 µg/m³2026-02-08: 22.3 µg/m³2026-02-09: 39.2 µg/m³2026-02-10: 40.3 µg/m³2026-02-11: 21.2 µg/m³2026-02-12: 7.9 µg/m³2026-02-13: 10.0 µg/m³2026-02-14: 15.8 µg/m³2026-02-15: 28.5 µg/m³2026-02-16: 5.8 µg/m³2026-02-17: 1.2 µg/m³2026-02-18: 24.2 µg/m³2026-02-19: 24.1 µg/m³2026-02-20: 20.8 µg/m³2026-02-21: 3.6 µg/m³2026-02-22: 2.1 µg/m³2026-02-23: 3.1 µg/m³2026-02-24: 16.2 µg/m³2026-02-25: 15.8 µg/m³2026-02-26: 14.7 µg/m³2026-02-27: 20.2 µg/m³2026-02-28: 7.5 µg/m³2026-03-01: 5.4 µg/m³2026-03-02: 5.4 µg/m³2026-03-03: 19.0 µg/m³2026-03-04: 22.7 µg/m³2026-03-05: 40.0 µg/m³2026-03-06: 38.0 µg/m³2026-03-07: 43.1 µg/m³2026-03-08: 52.6 µg/m³2026-03-09: 56.2 µg/m³2026-03-10: 54.7 µg/m³2026-03-11: 13.8 µg/m³2026-03-12: 1.0 µg/m³2026-03-13: 3.5 µg/m³2026-03-14: 1.8 µg/m³2026-03-15: 1.1 µg/m³2026-03-16: 1.5 µg/m³2026-03-17: 7.6 µg/m³2026-03-18: 12.8 µg/m³2026-03-19: 31.2 µg/m³2026-03-20: 15.0 µg/m³2026-03-21: 21.3 µg/m³2026-03-22: 40.1 µg/m³2026-03-23: 49.6 µg/m³2026-03-24: 43.9 µg/m³2026-03-25: 2.9 µg/m³2026-03-26: 0.2 µg/m³2026-03-27: 7.7 µg/m³2026-03-28: 3.9 µg/m³2026-03-29: 0.6 µg/m³2026-03-30: 0.8 µg/m³2026-03-31: 1.9 µg/m³2026-04-01: 11.6 µg/m³2026-04-02: 15.9 µg/m³2026-04-03: 7.0 µg/m³2026-04-04: 2.1 µg/m³2026-04-05: 1.4 µg/m³2026-04-06: 0.1 µg/m³2026-04-07: 1.1 µg/m³2026-04-08: 4.1 µg/m³2026-04-09: 16.9 µg/m³2026-04-10: 2.4 µg/m³2026-04-11: 6.0 µg/m³2026-04-12: 0.6 µg/m³2026-04-13: 8.0 µg/m³2026-04-14: 10.2 µg/m³2026-04-15: 15.4 µg/m³2026-04-16: 2.1 µg/m³2026-04-17: 5.2 µg/m³2026-04-18: 6.6 µg/m³2026-04-19: 0.6 µg/m³2026-04-20: 2.5 µg/m³2026-04-21: 5.2 µg/m³2026-04-22: 9.1 µg/m³2026-04-23: 10.9 µg/m³2026-04-24: 9.5 µg/m³2026-04-25: 12.8 µg/m³2026-04-26: 2.1 µg/m³2026-04-27: 2.0 µg/m³2026-04-28: 3.4 µg/m³2026-04-29: 1.2 µg/m³2026-04-30: 0.1 µg/m³2026-05-01: 0.8 µg/m³2026-05-02: 17.6 µg/m³2026-05-03: 24.5 µg/m³2026-05-04: 32.6 µg/m³2026-05-05: 6.2 µg/m³2026-05-06: 2.7 µg/m³2026-05-07: 0.1 µg/m³2026-05-08: 8.9 µg/m³2026-05-09: 11.8 µg/m³2026-05-10: 11.2 µg/m³2026-05-11: 0.1 µg/m³2026-05-12: 1.0 µg/m³2026-05-13: 0.2 µg/m³2026-05-14: 0.3 µg/m³2026-05-15: 0.5 µg/m³2026-05-16: 1.7 µg/m³2026-05-17: 15.1 µg/m³2026-05-18: 9.9 µg/m³2026-05-19: 9.1 µg/m³2026-05-20: 7.4 µg/m³2026-05-21: 5.3 µg/m³2026-05-22: 11.4 µg/m³2026-05-23: 24.6 µg/m³2026-05-24: 20.7 µg/m³2026-05-25: 3.6 µg/m³2026-05-26: 6.9 µg/m³2026-05-27: 6.8 µg/m³2026-05-28: 2.1 µg/m³2026-05-29: 13.8 µg/m³2026-05-30: 12.5 µg/m³2026-05-31: 9.2 µg/m³2026-06-01: 3.2 µg/m³2026-06-02: 4.5 µg/m³2026-06-03: 0.8 µg/m³2026-06-04: 1.0 µg/m³2026-06-05: 0.5 µg/m³2026-06-06: 2.9 µg/m³2026-06-07: 0.6 µg/m³2026-06-08: 2.5 µg/m³2026-06-09: 0.0 µg/m³2026-06-10: 0.1 µg/m³2026-06-11: 0.1 µg/m³2026-06-12: 1.4 µg/m³2026-06-13: 0.9 µg/m³2026-06-14: 0.8 µg/m³2026-06-15: 0.6 µg/m³2026-06-16: 6.6 µg/m³2026-06-17: 6.3 µg/m³2026-06-18: 2.1 µg/m³2026-06-19: 9.0 µg/m³2026-06-20: 4.0 µg/m³2026-06-21: 10.8 µg/m³2026-06-22: 0.2 µg/m³2026-06-23: 2.1 µg/m³2026-06-24: 14.1 µg/m³2026-06-25: 27.0 µg/m³2026-06-26: 16.8 µg/m³2026-06-27: 17.5 µg/m³2026-06-28: 8.9 µg/m³2026-06-29: 0.4 µg/m³2026-06-30: 0.3 µg/m³2026-07-01: 1.3 µg/m³2026-07-02: 2.5 µg/m³2026-07-03: 0.1 µg/m³2026-07-04: 3.1 µg/m³2026-07-05: 0.5 µg/m³2026-07-06: 1.4 µg/m³2026-07-07: 1.2 µg/m³2026-07-08: 1.0 µg/m³2026-07-09: 6.4 µg/m³2026-07-10: 6.3 µg/m³2026-07-11: 15.4 µg/m³2026-07-12: 9.9 µg/m³2026-07-13: 6.6 µg/m³2026-07-14: 6.6 µg/m³2026-07-15: 8.7 µg/m³2026-07-16: 7.0 µg/m³2026-07-17: 17.1 µg/m³2026-07-18: 9.3 µg/m³2026-07-19: 0.3 µg/m³2026-07-20: 0.2 µg/m³2026-07-21: 0.6 µg/m³2026-07-22: 0.4 µg/m³2026-07-23: 0.1 µg/m³2026-07-24: 1.9 µg/m³2026-07-25: 10.8 µg/m³2026-07-26: 4.1 µg/m³2026-07-27: 0.2 µg/m³2026-07-28: 2.8 µg/m³2026-07-29: 4.8 µg/m³2026-07-30: 7.8 µg/m³2026-07-31: 9.5 µg/m³2026-08-01: 1.4 µg/m³2026-08-02: 2.2 µg/m³2026-08-03: 6.4 µg/m³2026-08-04: 14.4 µg/m³2026-08-05: 0.3 µg/m³2026-08-06: 0.6 µg/m³2026-08-07: 0.5 µg/m³2026-08-08: 2.5 µg/m³2026-08-09: 2.6 µg/m³2026-08-10: 4.2 µg/m³2026-08-11: 0.2 µg/m³2026-08-12: 1.3 µg/m³2026-08-13: 2.4 µg/m³2026-08-14: 9.1 µg/m³2026-08-15: 10.2 µg/m³2026-08-16: 1.2 µg/m³2026-08-17: 0.1 µg/m³2026-08-18: 6.0 µg/m³2026-08-19: 1.0 µg/m³2026-08-20: 4.1 µg/m³2026-08-21: 0.7 µg/m³2026-08-22: 1.6 µg/m³2026-08-23: 3.0 µg/m³2026-08-24: 1.4 µg/m³2026-08-25: 3.6 µg/m³2026-08-26: 7.2 µg/m³2026-08-27: 27.6 µg/m³2026-08-28: 16.5 µg/m³2026-08-29: 1.4 µg/m³2026-08-30: 0.7 µg/m³2026-08-31: 0.4 µg/m³2026-09-01: 0.1 µg/m³2026-09-02: 1.4 µg/m³2026-09-03: 0.6 µg/m³2026-09-04: 0.3 µg/m³2026-09-05: 0.7 µg/m³2026-09-06: 1.2 µg/m³2026-09-07: 1.9 µg/m³2026-09-08: 0.3 µg/m³2026-09-09: 0.1 µg/m³2026-09-10: 1.2 µg/m³2026-09-11: 4.5 µg/m³2026-09-12: 7.1 µg/m³2026-09-13: 1.3 µg/m³2026-09-14: 4.4 µg/m³2026-09-15: 9.7 µg/m³2026-09-16: 0.0 µg/m³2026-09-17: 1.2 µg/m³2026-09-18: 0.9 µg/m³2026-09-19: 2.3 µg/m³2026-09-20: 0.3 µg/m³2026-09-21: 0.1 µg/m³2026-09-22: 1.7 µg/m³2026-09-23: 15.6 µg/m³2026-09-24: 1.1 µg/m³2026-09-25: 4.7 µg/m³2026-09-26: 12.1 µg/m³2026-09-27: 17.3 µg/m³2026-09-28: 12.0 µg/m³2026-09-29: 21.9 µg/m³2026-09-30: 12.1 µg/m³
Good 0–9.0Moderate 9.1+Unhealthy for sensitive groups 35.5+Unhealthy 55.5+Very unhealthy 125.5+Hazardous 225.5+No data

101 of 364 measured days were over the WHO 24-hour guideline.

Daily world rank

#1#2494OctNovDecJanFebMarAprMayJunJulAugSep

Rank on each day's board (1 = most polluted city that day).

2026 against 2025, month by month

15Jan 2026: 28.6 µg/m³JanFeb 2026: 23.6 µg/m³FebMar 2026: 19.3 µg/m³MarApr 2026: 5.9 µg/m³AprMay 2026: 9.0 µg/m³MayJun 2026: 4.9 µg/m³JunJul 2026: 4.8 µg/m³JulAug 2026: 4.3 µg/m³AugSep 2025: 10.7 µg/m³Sep 2026: 4.6 µg/m³SepOct 2025: 5.3 µg/m³OctNov 2025: 13.8 µg/m³NovDec 2025: 17.1 µg/m³Dec

Faded bars: 2025. A month shows once it has 10 measured days.

This week against past years

This weekThis week: 11.6 µg/m³11.620252025: 15.9 µg/m³15.9

Mean PM2.5 for 24 Sept to 30 Sept in each year. Dashed line: WHO 24-hour guideline.

Monitors

StationOperatorType
BloemendaalCC BY 4.0CleanAirLow-cost
HaarlemCC BY 4.0NetAwareLow-cost
HeussensstraatCC BY 4.0AirGradientLow-cost

No reference monitor here, so the value is the median of low-cost sensors (at least two reporting each hour). Low-cost sensors can read high in humid air. Data via OpenAQ; licences as listed. How we rank. Embed this on your site.

Other cities in The Netherlands

Schiedam 7.7Medemblik 7.1Breda 7.1Barneveld 7.0Venray 6.9Amsterdam 6.7Tilburg 6.6IJsselstein 6.6Velserbroek 6.6Utrecht 6.5's-Gravenzande 6.5The Hague 6.5

30-day averages, µg/m³. All of The Netherlands →

Updated 2026-10-01 05:07 UTC. Values are PM2.5 in µg/m³ (fine particles), the median of each city's monitors.