.Police are advising people not to travel unless it is essential after heavy snow over night.
Motorists are being warned they 'should not put themselves in unnecessary danger' after the North East took the brunt of the snowy weather in the last 24 hours.
Officers from Northumbria, Durham and Cleveland forces have issued warnings.
A spokesman for Durham Constabulary said: "Police are advising drivers not to travel unless absolutely essential.
"Following heavy snow overnight, road conditions are treacherous, and users are urged not to underestimate the difficulty of the driving conditions.
"At present, the A66 is closed between Scotch Corner and Bowes, and further road closures may be put in place throughout the rest of the day.
"If you are using the roads, please take extra care. Allow extra time for your journey, keep your distance from the vehicle in front, and make sure your car is fully cleared of snow before setting off."
A Northumbria Police spokesman said: "Another night of heavy snow fall has led to a number of issues on the roads this morning.
"Due to the freezing cold temperatures there is also a lot of black ice underneath that blanket of snow.
"Gritters have been out through the evening and again this morning but the continuous snow fall has led to very bad conditions.
"All the major routes are passable with care but there will be congestion, there will be delays and it will be slippy.
"Not only are the roads in a bad condition but the visibility is very poor due to the blizzard conditions.
"A number of schools have been closed and our message to the public is simple – do not leave the house if you don’t have to.
"If you do then leave plenty of time for your journey, slow right down, leave plenty of space in front and please stay patient.
"We recognise it may be frustrating but people should not put themselves in unnecessary danger."
A Cleveland Police spokesman said: "The snow is expected to cause some travel issues this morning. Only drive if essential!"
"DO NOT leave your vehicles defrosting unattended.
"Stick to the main roads where you can and avoid exposed routes."
Highways England’s Senior Emergency Planning Manager in the North East, Andrew Charnick, said: “Our gritting teams have been out treating the roads throughout the day and will continue to spreading salt 24 hours a day to keep the roads moving.
“Drivers should plan their journeys, monitor weather reports and pack a snow kit of blankets, food, water and a shovel if they really need to travel. You should avoid driving during heavy snow if at all possible.
“Our advice is to keep your distance and reduce your speed because, even in conditions that seem normal and when the snow is not settling, it can be slippery if ice patches have formed, or where fresh salt has not been worked into the carriageway.”