Hurricane Lorenzo has strengthened into a category five storm in the central Atlantic Ocean, making it the strongest storm ever observed so far north and east in the Atlantic basin.
The US National Hurricane Centre said that the storm has maximum sustained winds of 160mph.
The tail-end of the 600-mile wide storm will batter Britain with 150mm of rain - with the Met Office branding it a "real beast".
Lorenzo is moving north at 10mph and is centred about 1,410 miles southwest of the Azores, a Portuguese island chain.
There are no coastal watches or warnings currently in effect, although forecasters expect the storm to remain strong as it approaches the Azores over the next few days.
Met Office forecaster Steven Keates said: "Lorenzo is a real beast of a storm.
"It will be one of Europe's strongest ever tropical storms, as the Azores are part of Europe.
"After reaching the Azores on Tuesday, Lorenzo is expected to move to the UK by Thursday - bringing a couple of days with potentially worse conditions than this weekend.
"There are scenarios from gales to storm-force 70mph-plus gusts, but there's uncertainty.
"Big waves and heavy rain are likely, with the west most likely to be affected.
"Before then, five or six inches' rain will fall between Saturday and Tuesday in the wettest places.
"It's clearly enough for flooding concerns.
"People should keep up-to-date with warnings and consider their travel options.
"The south-west looks wettest, but other parts will see rain, focused on Sunday then Monday night into Tuesday.
"It will be windy across the South and Midlands, with gusts up to 60mph on Sunday and 50mph from Monday night, windiest on the south coast.
"The season's first snowfall is possible on Wednesday on Scotland's mountains, with accumulating snow on the highest ground.
"-2C on Tuesday night is forecast in northern England and Scotland, and 0C in the South."