Saharan dust is a mixture of sand and dust from the Saharan desert, which can be blown further afield by strong winds – in this case, from Storm Celia.
The Met Office says the dust can reach as far as the UK if the ‘winds in the upper part of the atmosphere are blowing north, the dust can be carried as far as the UK’.
“Once it is lifted from the ground by strong winds, clouds of dust can reach very high altitudes and be transported worldwide, covering thousands of miles,” it explains on its website.
In order for this dust to come down to the ground, it needs to be washed out of the sky by rain – with raindrops collecting particles of dust as they fall. When the rain lands and eventually evaporates, a layer of dust is then left behind.
Earlier this morning (Wednesday 16 March), the Met Office tweeted to say that the dust may fall to the ground.
It said: "We can see the #SaharanDust that has pushed across Spain and France, into southeast England.
"Whilst this dust is mostly about 2km above ground level, some deposits may fall to the ground, especially during today's rain in southern parts of the UK."
Saharan dust can sometimes pose a health risk, including to people with asthma, with atmospheric scientist Dr Claire Ryder from the University of Reading saying: "Air quality may be slightly lower than usual due to the dust particles in the air."
However, the Met Office's Richard Miles said no air quality warnings have been issued, although warned that people may find dust left on their cars.
Miles said: “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.”
Ryder added: “The main plume is forecast to remain over the continent with only the weaker edges grazing southern England. Dust amounts will likely be significantly lower over England compared to extremely dusty conditions currently being experienced over Spain and France.
“By evening the dust will have moved eastwards towards the Netherlands and Germany.”
A number of European countries have seen their skies turn an eerie shade of orange, including in Spain and France.
Switzerland has also been affected, with images from a Meteo Suisse webcam at the top of La Dôle mountain showing sepia skies and what appears to be a buildup of sand on the lens.
Social media users also shared images of the 'unreal sky' at lunchtime yesterday, with one writing: "Orangey sand tinted sky this morning in Switzerland coming from the sand dust in the Sahara dessert."
Someone else tweeted: "The Sahara dust has been giving a Mars look to parts of Switzerland and Australia over the last few days, and there is reports the snow has been falling with a orange haze too it."Featured Image Credit: Reddit u/Nightrach; LAURENT GILLIERON/EPA-EFE/Shutterstock