The deep freeze hitting Britain is poised to cause travel chaos in the morning as temperatures that have fallen as low as minus 8C are to continue.
Freezing fog and widespread frost will cause rush hour problems with possible delays to flights at airports.
Temperatures plummeted to as low as minus 8C (17.6F) in parts of Hampshire and Essex on Sunday morning, the Met Office said.
Slightly warmer conditions are expected overnight, ranging between minus 4C (24.8F) and minus 6C (21.2F) in the south east.
Northern Ireland, some of Scotland and northern England will also start the week with a “sharp frost”.
Drivers have been urged to prepare for hazardous conditions as Britain continues to be gripped by sub-zero temperatures.
The Met Office has issued a yellow be aware warning for fog in London, the south west, south east, and some eastern parts, valid from 1am to 10.30am on Monday
Forecaster Steven Keates said:
“In this area we are likely to see some dense freezing fog patches developing, particularly through the early hours, which could impact some travel through the course of tomorrow’s rush hour.
”There will be difficult driving conditions and delays at some airports - including the London airports.”
Freezing temperatures and a blanket of frost could also create slippery driving conditions.
Mr Keates said:
“We ask everyone to be aware of the potential impact the fog will have on the roads.
”Take it steady, allow a bit of extra time for your journey.
”If you have got an early morning flight it might be worth double checking, just to make sure there are no delays at the airport.”
Heathrow airport said fog was expected to cause some disruption to flights on Monday.
The foggy conditions look set to continue into Tuesday but will move further east and north into the Midlands and east of England.