Saharan dust is expected to settle in parts of the UK as the country basks in what could be the hottest day of the year.
Forecasters predicted that temperatures could soar to up to 19C (66.2F) in parts, making it hotter than Barcelona and Ibiza.
Officials have warned of moderate to high air pollution in the South East as southerly winds sweep dust from the Saharan region northwards.
Marco Petagna, from the Met Office, said parts of Kent and the far South East would see the highest levels of pollution.
"On Thursday, dust from the Sahara region was lifted up into the atmosphere", he said. "At the moment, certainly across the south of the UK, we've got southerly winds that's allowed that dust to transport northwards towards the UK.
"And with outbreaks of rain developing at times over the next couple of days, some of that will get washed out of the atmosphere and give a slight deposit of dust on cars."
The pollution could pose a potential health risk to vulnerable groups.
At-risk individuals, including those with lung and heart problems, should "reduce strenuous physical exertion" if they are in an affected area, the Department for Environment, Food and Rural Affairs said.
Temperatures peaked at 15.8C (60.4F) in Holbeach, Lincolnshire, on Saturday, and are expected to rise to between 18C (64.4F) or 19C (66.2F) in the South East on Sunday.
But forecasters predicted showers, particularly in northern and eastern England, Scotland and Northern Ireland.
Sophie Yeomans, from the Met Office, said average temperatures for early April were normally around 11C (51.8F) or 12C (53.6F), while this year's highest recorded temperature was 18.7C (65.6F) in Braemar, Aberdeenshire, in March.
"If we reach 19C that would make it the hottest day of the year," she said.
"But it's a bit of a mixed bag - in Scotland and Northern Ireland and further north, there is some rain around for most of the day. In Scotland and in the North, it will be fairly chilly and highs will only reach 11C.
"Further south, in England and Wales, it's mainly going to be sunny spells and patchy cloud. Western areas might just see some showers in the evening that will be quite heavy.
"The best of the weather is going to be in the South East."
The warmer climate is due to tropical continental air being brought into the UK through a change in wind direction.
But it will not last, with the Met Office warning that early next week will become "fairly unsettled" with heavy showers. Temperatures could still reach 17C (62.6F) in places.
Bookmakers were predicting the hottest day of the year this weekend, but seem sceptical that this April will be the hottest on record, only offering odds of 100/1.