Emergency services in Kent have warned people not to make unnecessary journeys as freezing temperatures created dangerous driving conditions.
The snow and ice made driving conditions treacherous in Kent
Several accidents were reported in the county with the M2 partly shut for some time after a crash in which a man died.
More than 460 schools in Kent were closed on Thursday with staff and pupils unable to travel.
Operation Stack saw the coastbound M20 closed at one stage from Maidstone to Folkestone, between junctions 8 and 13.
Weather forecasters said the temperatures could be as cold as minus six on Thursday night, with freezing temperatures expected to continue into Friday with more snow showers also predicted.
Kent Police advised people not to make unnecessary journeys and the ambulance service in the county said people should stay indoors.
A Highways Agency spokesman said: "All road users are asked to check the weather forecast and road conditions before they set out.
"In severe weather, delaying a journey by a few hours could make the difference between a completed trip and a difficult drive in poor conditions."
Operation Stack brought lorries on the snowy M20 to a standstill
The M2 was closed London-bound between junctions 5 and 6 until 1330 GMT after a collision in which an 18-year-old was killed.
The M20 was partially closed due to a jack-knifed lorry before Operation Stack, the traffic control move which turns the M20 near Dover into a lorry park, was introduced.
Phase two of the operation was later implemented, meaning the motorway was closed coastbound from Maidstone to Folkestone, though it re-opened between junctions 9 and 11 at about 1800 GMT.
Police said the move was necessary because of the weather and problems at the Channel Tunnel.
Public transport experienced delays with all Arriva buses in Kent cancelled.
South Eastern Trains said all services were running but said there were 30 minute delays across the network.
'Very cold again'
It said during the rush hour, priority would be given to trains heading from London to Kent.
Kent Police said the number of vehicles abandoned due to the icy conditions was also a problem.
The Highways Agency said all major routes had been treated by Thursday morning.
Nicky Bullett, from Kent County Council, said: "Unfortunately it's going to be very cold again tonight so where there are untreated roads, it will be like sheets of ice."
There were power cuts on the Isle of Sheppey, Faversham and surrounding villages as well as in the Maidstone area.
Court sittings in Maidstone were suspended because of the weather.