The tidal surge is being caused by 50mph winds in the North Sea, an unusually high tide and an area of low pressure off the East Coast.
Tens of thousands of householders are today preparing for some of the worst coastal floods in decades.
Sea levels could rise up to 9ft this morning along part of the East Coast, putting lives at risk.
Sea defences in Great Yarmouth and Lowestoft could be breached around 7am, sending a torrent of salt water into the towns.
• Eight severe flood warnings issued by Environment Agency
• Surge expected to hit east coast in next 12 hours
• Police on standby to evacuate homes
• Dartford Creek and Thames barriers closed
Police and fire services were last night preparing to evacuate thousands of homes. Householders were stocking up on sandbags and emergency provisions.
The Norfolk Broads, Essex and northern Kent could also be hit, and the entire coast from Immingham in Humberside to Margate in Kent has been told to be on alert.
The Environment Agency, which issued eight severe flood warnings, last night said it was "gravely concerned" about the threat.
England suffered one of its worst peacetime disasters in 1953 when floods battered the east coast, claiming hundreds of lives.
On the night of January 31, the sea swept up to two miles inland, with huge tides surging down the coast between the Tees and the Thames.
By the morning, 307 people in coastal towns and villages had lost their lives. Around 24,000 homes were damaged and more than 30,000 people had been moved to safety.