LONDON — Even before the first snowflake had fallen, alarm bells were sounding across Britain.

“Beware Beast From the East: It Will Kill,” one tabloid warned.

“Army on standby as heavy snow to cripple Britain in –15C weather hell,” another said.

Bold red signs went up in shop windows, prompting panicked Brits to empty supermarket shelves: “SNOWMAGGEDON! Stock up on essentials now.”

They were describing a storm known as the Beast From the East, a polar vortex that brought freezing temperatures and snowstorms to parts of Europe this week, including to cities like Rome and London that rarely see snow.

Some noted that as the cold descended on Europe, the Arctic was witnessing one of its warmest winters ever. Last Sunday, as the temperature in Britain fell to 23 degrees Fahrenheit (minus 5 Celsius), northern Greenland was at 43 degrees.