Brace yourselves, Londoners: a dust storm is coming.
The Department for Environment, Food and Rural Affairs (Defra) has issued a warning that air pollution could be moderate or high as dust from the Sahara is expected to blow across parts of England and Wales.
Children, elderly people and adults with lung and heart problems have been warned to take things slow tomorrow. They have been told to reduce any physical exertion, particularly outdoors, and watch out for any difficulty breathing.
People with asthma may need to use their inhaler more often, Defra added.
The areas worst affected include London and the South East, with Norfolk and Lincolnshire likely to get the brunt of the dust.
Thursday will be the most severe day, but the dust is expected to cause a rise in pollution levels into Saturday.