The UK is set to be hit by dusty, orange skies on Wednesday as an unusual weather phenomenon reaches the country.

In the worst case scenario, people may discover a layer of red dust covering cars and streets, as seen in Spain.

A mass of hot air crossing from the Sahara has seen Spain and parts of France affected by orange, yellow-tinted skies and small heaps of sand. 

The UK is likely to get a milder version of the weather event while forecasters predict more accumulation of dust in the Netherlands and north-western Germany.

Denbighshire Free Press: A slightly yellow sky seen on Wednesday morning in Portsmouth. Photo via Andy Dixson.A slightly yellow sky seen on Wednesday morning in Portsmouth. Photo via Andy Dixson.

Why is the sky orange today?

Hot air in the Sahara desert has lead to dust being dumped across the Mediterranean and now parts of the UK.

Known as Storm Celia, the Met Office said the dust cloud, which is 2km above ground level, may fall during showers in southern parts of the UK in the afternoon.

Forecasters say the impact is “unlikely” to be significant, with the dust potentially most visible at sunset.

It comes as parts of southern Spain have been blanketed following a thick plume which has turned skies orange, with satellite images clearly showing the dust over France.

The wave of hot air has also affected the air quality in areas north of Madrid, as far west as in Spain’s Canary Islands in the Atlantic Ocean, where these events are more frequent, and in the Balearic Islands in the Mediterranean.

Many Spaniards awoke on Tuesday to find a layer of red dust covering terraces, streets and cars.

Spain’s weather service described the dust storm from the Sahara as “extraordinary and very intense”, while adding that it was unclear if it was the worst episode of its kind on record.

Paris was among the cities in France affected by dust, leaving the city's 18th arrondissement "covered with a fine layer of orange residue".

Caroline Harrap, a freelance journalist based in Paris, said: "Although I've seen this kind of weather phenomenon before, I've never experienced it quite on this scale. Here in Paris, the light took on a very strange, almost ethereal quality. So, I went outside to have a closer look and noticed that everything was covered with a fine layer of orange residue. At the time, I thought it must be caused by the building works down the street. It was only afterwards I discovered that, rather more romantically, it was actually due to a Saharan sandstorm."

Should I take any precautions?

In Spain, emergency authorities recommended citizens use face masks if they go outside and avoid outdoor exercise - though it is unlikely that the UK will be affected quite as bad.

Spanish officials issued extremely poor air quality ratings for Madrid and a large swathe of the country.

Spain’s national air quality index qualified the capital and large parts of the south-east coast as “extremely unfavourable” – its worst rating.

The sky in the capital and other cities had a gritty tinge to them. Visibility in Madrid and cities like Granada and Leon was reduced to 2.5 miles, the weather service said.

Speaking about Storm Celia's impact on the UK, the Met Office's Richard Miles told PA: “Storm Celia over Spain is indeed pulling a dust cloud up from the Sahara, which could potentially reach as far as the south of the UK.

“However, we don’t expect significant impacts – the most likely would be on the cloudscapes at sunset, but as conditions are likely to be generally overcast and wet for much of the day this is unlikely to amount to much. There are no air quality warnings.

“People in the south might find a bit of dust left on their cars as the rain washes it out of the skies today.”

Is the orange sky and sand caused by climate change?

Ruben del Campo, a spokesman for Spain’s weather service, said that while it was unclear if climate change had a direct link to this episode, the expansion of the Sahara desert over the past century has increased the potential for larger dust storm events in Europe.

He also said that the increasingly turbulent weather patterns linked to climate change could play a part.

“There are many concerns regarding the impact that climate change is having on the patterns of the frequency and intensity of the storms that favour the arrival of dust to our country,” Mr del Campo said.