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What do the forecasts mean? 

Defra’s air quality forecast provides air quality information based on five pollutants: ozone, nitrogen dioxide, sulphur dioxide, PM2.5 and PM10 particles that can have an impact on your health.

The forecasts use the Daily Air Quality Index (DAQI) that is designed to show complex air quality information on a simple 10 point scale.  The DAQI uses a combination of numbers (1-10), words (low, moderate, high and very high) and colours (green/yellow/orange/red/purple) to communicate the levels of pollution expected.  Each of the bands/levels of the DAQI has associated health information and advice for the general public as well as those that may be more sensitive to air pollution, so please check the DAQI page for more information.

The forecast for today is valid until midnight and then the forecast for tomorrow and subsequent days are for 24hr periods from midnight to midnight. New forecasts are produced each morning for all 5 days of the forecast.  As with weather forecasts, air quality forecasts are more uncertain for longer forecast periods but these provide a good outlook of likely future events.

Forecasts are displayed on the UK map but are also available for 5000 specific locations over the UK.  By searching for your postcode you can see air quality forecasts for the locations of most interest to you. You can find the DAQI for the area of the UK where you will be spending most time and relate the index value to the health advice. The 5000 locations represent rural and urban background locations and therefore may not capture conditions close to busy roads where air pollution is often higher. Certain weather conditions are more likely to lead to a build-up of local pollution near busy roads and the text forecast will highlight when these conditions are likely.

Other ways to find out about air pollution forecasts

  • Freephone 0800556677
  • National newspapers
  • TV and Radio Weather Forecasts

Page last modified: 27 March 2014