The Department for Environment, Food & Rural Affairs in its latest forecast shows that there could be very high pollution levels for a time in the far south-east of England, due to a flow from the south.
Generally in the south-east levels of air pollution are forecast to become high.
The DEFRA advice when pollution levels are very high is for adults and children with lung problems, adults with heart problems, and older people, to avoid strenuous physical activity.
People with asthma may find they need to use their reliever inhaler more often.
During Saturday, clearer Atlantic air is due to spread across all areas bringing levels down over the weekend back to generally low pollution.