The Met Office has forecast the highest 10 out of 10 level of air pollution in the capital for tomorrow and Wednesday.
Motorists work up to find their cars covered in a thin layer of dust after overnight showers deposited the sand on much of London.
Southerly winds from north Africa brought the fine sand over southern England after it was swept up in a desert storm late last week.
Paul Hutcheon, Deputy Chief Forecaster at the Met Office, said: “We usually see this happen several times a year, particularly in summer when you get these big dust storms in the western Sahara and the southerly winds to bring that dust here."
