Downgraded from a hurricane overnight, Ophelia caused two deaths in Ireland on Monday, where it was the worst storm in half a century.
While winds were moderate in the British capital, the yellow sky surprised Londoners, many of whom posted pictures on social media.
"As Ophelia has come up from the Azores, the storm has picked up Saharan dust from North Africa and picked up dust from wild fires in Spain and Portugal," a spokeswoman for Britain's Met Office said.
"This yellowish hue is from the dust that is high up in the atmosphere and the blue element of the sunlight is scattered by the dust but the red element gets through so the sun appears redder and you get this sort of yellowish tinge," she said.
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