Copenhagen Jagtvej NO₂ forecast

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Hourly nitrogen dioxide forecast for the Jagtvej roadside monitoring station in Copenhagen.

NO₂ in µg/m³ for each hour, Copenhagen time. White marks this station's typical level, about 12 µg/m³. Cleaner More polluted

The last two days and the next one

Measured values lead into the current forecast. The gap before the forecast starts is the time measurements take to arrive, about three hours. The shaded band shows the typical size of the forecast error. The dashed line shows what the model predicted six hours in advance, for hours that have since been measured.

Measured Forecast Typical error Predicted 6 hours ahead

How close it has been

How it works

The forecast describes the air at one roadside monitoring station on Jagtvej, not the whole street. Every part runs on its own, on free infrastructure, and nothing on this page is updated by hand.

  1. 1Measure

    Hourly NO₂ from official monitoring stations and weather data are collected into a Postgres database every hour.

  2. 2Freeze

    Each week the data is saved as a versioned snapshot, so every model can be traced to the exact data it learned from.

  3. 3Retrain

    A new model is trained every week. It replaces the current one only if it is at least 2% more accurate on the same recent weeks.

  4. 4Forecast

    Every hour, the current model predicts the next 24 hours from the latest measurements and the weather forecast.

  5. 5Check

    Daily checks watch data freshness and live accuracy, and a weekly report flags unusual inputs.

About NO₂

Nitrogen dioxide is one of the main air pollutants in cities. It changes hour by hour with traffic and weather, which is what makes it worth forecasting.

What it is

A reddish-brown gas formed when fuel burns at high temperature. Engines mostly emit nitrogen monoxide (NO), which turns into NO₂ within minutes as it reacts with ozone in the air. That is why levels are highest right next to busy roads and fall off quickly with distance.

Where it comes from

Road traffic is one of the major sources in cities. Levels rise in rush hours and on calm days when the air mixes poorly, and drop when the wind picks up.

Why it matters

High levels irritate the airways and can make asthma worse. Long-term exposure is linked to respiratory disease. Children, older people and people with asthma or heart and lung conditions are the most sensitive. NO₂ also helps form ozone and fine particles.

Reference values for NO₂, in µg/m³
Annual average 24-hour average 1 hour
WHO guideline (2021) 10 25 200
EU limit value today 40 None 200
EU limit value from 2030 20 50 200

The WHO 24-hour value should not be exceeded on more than 3 to 4 days a year. Today the EU 1-hour limit may be exceeded up to 18 hours a year. From 2030 that falls to once a year, and the 24-hour limit may be exceeded up to 18 days a year.

Using the forecast

If you have asthma or another lung condition, the forecast can help you plan outdoor exercise for cleaner hours. Walking or cycling on quieter streets, even one block away from heavy traffic, also lowers what you breathe.

This page gives general information only. It is not medical advice. Follow guidance from your doctor or the health authorities.