The sky over England appeared to glow orange and yellow today in a strange phenomenon caused by Storm Ophelia.
Hundreds of people marvelled at the bizarre sight which lit up London in sepia and led many to joke that the apocalypse had arrived.
Stunning images of the so-called "red sun" were shared by people across the country as they compared the weather to looking through tinted glasses.
According to experts at the Met Office, the rare spectacle was caused by Storm Ophelia pushing warm air from Africa northwards, and with it came Saharan dust.
As the air moved north towards Ireland and the UK, it gathered smoke and tiny debris from recent wildfires in Spain and Portugal.
Why does dust affect the colour of the sky?
When there are dust particles in the air, these obstruct the path of incoming sunlight. Light which is shorter in wavelength, like blue and violet, are unable to penetrate through the atmosphere, so are scattered away.
But light of longer wavelengths, including yellow, orange and red light, is still able to get through – thus giving the warm tint as seen today.
The fascinating explanation also accounts for why sunrises and sunsets are often red and orange: when the sun is lower in the sky, the light has to pass through more particles in the atmosphere.
Red sunsets are often observed best from a beach, because of the salt particles suspended in the air above the sea.
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For the majority of people the dust is not thought to pose a health risk, but sufferers of severe asthma are being urged to stay indoors where possible.
Sonia Munde, head of the helpline at Asthma UK, said: "We are deeply concerned about the toxic air from Saharan dust that Hurricane Ophelia has churned up, as this could pose a severe risk for the 5.4 million people in the UK who have asthma.
"Winds picking up dust and particles in the air could trigger potentially fatal asthma attacks."
Today's movement of air up from the continent saw temperatures rise, with highs of 22C in parts of southern England today, including London.
Ophelia, which had been speeding over the Atlantic as a category three hurricane before being downgraded to a post-tropical storm, hit the south west tip of Ireland on Monday morning.
On Monday evening, the storm arrived in west Wales and Northern Ireland, where tens of thousands of homes are without power.