9:38am UK, Wednesday May 28, 2008

If your car is covered with a layer of sand or dirt today, it may have come all the way from the Sahara desert.

The Sahara - or the UK?

The UK does not normally receive airstreams coming from Africa - usually they travel in from the Atlantic - but winds today are blowing in from the desert region.

"As wind blows across the Sahara it carries off particles of sand - tonnes of it every day," said Sky News weather presenter Francis Wilson.

"The warm airstream carries the sand thousands of miles, and dust has already fallen over Spain and France.

"There could well be some Saharan dust mixed up in the rain that is going to fall in England and Wales.

"It's a pretty rare event - the dust reaches us only once or twice a year."

The Saharan dust itself is not responsible for the thunderstorms forecast for Britain today, but the hot air from Africa is what will provoke the torrential downpours.

Areas affected by heavy rain may experience localised flooding, the Met Office has warned.

But there is good news for later this week, when the Sun is expected to come out and temperatures are forecast to reach 22C in some parts of Britain.