Nefarious Martians or the apocalypse were among the reasons floated for an unusual atmospheric phenomenon in London on Monday.
The sky over the capital turned a hazy yellow, causing confusion among residents.
“Guys why is the sky in London yellow? Dust storm? Martians?” asked one Twitter user.
Another queried: “Why is the sky yellow in London right now? Can someone explain? Is this the end of days?”
Meteorologists said a possible cause was dust brought up from the Sahara desert by southerly winds.
Oli Claydon, a Met Office spokesperson, told The Independent: “With the wind coming from the south we have had some Saharan dust brought across the UK at very high altitudes, [though] not at sea level.
“That’s helped to cause some notably vibrant sunrises and sunsets.
“If anything, it’s actually moving away.”
A similar but significantly more extreme such event followed the impact of ex-Hurricane Ophelia in 2017, when skies turned a deep ochre and the sun was visible as a deep red disc.
A yellow tint to Monday’s overcast skies was also reported in Essex.
In a blog post last week Nasa’s Earth Observatory noted that a plume of Saharan dust was heading for Europe.
Every year, some 180 million tons of dust blow out of northern Africa, the space agency said.