Londoners will have to wrap up this week with temperatures in the capital expected to fall to -1C, according to the Met Office.
Some parts of the country will experience their coldest night this year as icy winds blow in from the Arctic. Rural areas of Scotland and Northern Ireland could plunge below extremes of -10C and even -15C.
"It only has to get past minus 9C (18.5F) and we'll have the coldest night for winter," said the Met Office's operational forecaster Calum MacColl.
The record was set on December 27 in Cromdale, Moray.
"As we lead our way into the coming days again, we've got snow warnings out for much of northern and eastern Scotland," he said.
"It's going to be pretty cold all week."