Pollution Forecast
Air quality does vary day to day and is affected by weather conditions.
The Department for the Environment, Food and Rural Affairs (Defra) provides publicly available air pollution forecasts 
, similar to weather forecasts, they're provided daily and with 5 day forecasts. These can be used by the public especially those with existing health problems that may be more affected by short term peak in poor air quality.
The forecasts use the Daily Air Quality Index (DAQI) that is designed to show complex air quality information on a simple 10 point scale 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.
Forecasts are displayed on a 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.