Netherlands · The summary is refreshed every 15 minutes.
November 11
The air is moderate now
Leiden
4°C
Cloudy
1003
hPaAtmospheric
pressure
82%
Humidity
Leiden, November 10, 2026: daily mean PM2.5 36 µg/m³ (9 sensors), level “Elevated” — as in the Atmy Data Hub. Now (23:00 local time): 35.3 µg/m³. Open methodology and data in JSON: Methodology and data sources · JSON
Right now in Leiden, PM2.5 averages 35.3 µg/m³ — “moderate” on the US EPA scale (approximate, from hourly readings). Mean of 9 sensors from Sensor.Community, AirGradient, readings from 22:48–22:58 local time (21:48–21:58 UTC), summary prepared at 23:00 local time. Median: 33.7 µg/m³; range across sensors: 19.7–50.3 µg/m³.
In Leiden the air is moderate 🟡 AQI 100. Higher than three hours ago. ☁️ +4 °C · No precipitation · Wind 1 m/s
In Leiden the air is moderate right now (approximate, US EPA scale). From 10:00 to 23:00 local time the city mean PM2.5 rose from 30.3 to 35.3 µg/m³.
Light wind (1 m/s) in the evening or at night, as the air cools, possibly traps particles near the ground (a temperature inversion). Cold weather (4°C) possibly means more heating, a common source of particles.
Weather now: cloudy, 4°C, wind 1 m/s, humidity 82%. Precipitation is expected around 07:00; it may wash particles out. By 10:00 the temperature will be about 8°C.
Written automatically at 23:00 local time (22:00 UTC) from sensor measurements and the weather forecast. Values are approximate; hypotheses are marked.
1 m/s
Wind, ENE
0 mm
Precipitation today
36 µg/m³ Elevated
Daily mean PM2.5 on November 10, 2026 (00:00–24:00 UTC = 01:00–01:00 UTC+1): 36 µg/m³ from 9 sensors that passed the quality check — the same value as in the Atmy Data Hub.
27/100Low · An estimate of weather conditions · not a PM2.5 forecast
8°/4°
Index by time of day
43/100Moderate
Night
Morning
Day
Evening10°/2°
Index by time of day
61/100Moderate
NightMorningDayEvening11°/9°
Index by time of day
39/100Moderate
NightMorningDayEvening9°/2°
Index by time of day
42/100Moderate
NightMorningDayEvening11°/2°
Index by time of day
42/100Moderate
NightMorningDayEvening11°/8°
Index by time of day
19/100Low
NightMorningDayEveningForecast of conditions that trap pollution near the surface
4°
Cloudy. Feels like 2°C
5°C87%7°C77%
4°C84%1m/sWind from the ENE
4m/sWind gusts
Wind force: 1
Light wind is expected over the next few hours.
Netherlands
8°C4°C10°C2°C11°C9°C9°C2°C11°C2°C11°C8°C9°C5°C10°C7°C10°C6°C8°C5°C
Highest current reading: 50.3 µg/m³ (SC #96904). Lowest: 19.7 µg/m³ (SC #62238). The list shows every sensor, highest first.
Source: atmy.ai monitoring network
Sensors in the summary by network: Sensor.Community — 8 sensors, AirGradient — 1 sensor.
Atmy shows the networks’ readings after the Data Hub’s quality check: test devices and sensors that fail it are left out.
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All sensors on the map, by city as the map assigns them; the city’s values count only the sensors that pass the Data Hub’s quality check.
Daily mean PM2.5 of the city sensors, µg/m³
Click a day to see its date and value.
An Atmy card with the air quality in Leiden now: it is refreshed every 15 minutes and links to this page. Paste the code into your site.
Netherlands · City ranking · All pilot cities
Daily mean PM2.5 on November 10, 2026 (00:00–24:00 UTC = 01:00–01:00 UTC+1): 36 µg/m³ from 9 sensors that passed the quality check — the same value as in the Atmy Data Hub.
Right now in Leiden, PM2.5 averages 35.3 µg/m³ — “moderate” on the US EPA scale (approximate, from hourly readings). Mean of 9 sensors from Sensor.Community, AirGradient, readings from 22:48–22:58 local time (21:48–21:58 UTC), summary prepared at 23:00 local time. Median: 33.7 µg/m³; range across sensors: 19.7–50.3 µg/m³.
The current level is “moderate” (US EPA scale, approximate). Unusually sensitive people should consider reducing prolonged or heavy exertion outdoors. This is the standard guidance of the scale, not medical advice.
Highest current reading: 50.3 µg/m³ (SC #96904). Lowest: 19.7 µg/m³ (SC #62238). The list shows every sensor, highest first.
From Atmy sensors and connected public networks (citizen, experimental and government monitors), aggregated by Atmy. Values are approximate; see the methodology.
The summary is rebuilt every 15 minutes from the latest reading of each sensor, each no older than one hour.
The daily value is the Data Hub’s: the mean of the city’s sensors that passed the nightly quality check, each with at least 12 valid hours, and only with sensors at four places 500 m apart; days are UTC.
“Now” uses the same sensors and rule: the mean of their latest readings, each at most 60 minutes old, shown only with sensors at four places 500 m apart reporting.
Source: public Atmy monitoring data. Methodology and data sources · Data terms
