Stagnant air and light winds are trapping pollutants with government agencies predicting the worst of the dirty air could be over eastern England.
Local forecasters @NNweather confirmed: "Air pollution levels will be higher in parts of the county tomorrow.
"Anyone with sore eyes, a cough or sore throat should consider reducing physical activity, particularly outdoors."
In London, Mayor Sadiq Khan has issued the capital's first pollution alert since since August 2020 and advised drivers to avoid unnecessary journeys to avoid adding fumes to the air.
The Met Office supplies an air quality forecast for the Department of Environment, Food & Rural Affairs based on five key pollutants — ozone, nitrogen dioxide, sulphur dioxide, PM2.5 and PM10 particles that can have an impact on your health.
Forecasts use the Daily Air Quality Index (DAQI) designed to show complex air quality information on a simple scale from nought, the lowest, to ten.
Predictions for parts of Northamptonshire for Thursday (March 24) are rated at seven, rising to eight over Wellingborough, Rushden, Raunds on Friday. Levels drop back to around four on Saturday.