A warning of sub-zero temperatures and snow has prompted police to issue safety advice to drivers.

Motorists are being warned of icy roads as temperatures are predicted to fall as low as - 4C on Friday.

Managers at the Royal Sussex County Hospital in Brighton have been holding emergency meetings this week to ensure they are as prepared as possible.

Plans include working out which staff have four-wheel drive cars so they are able to get into hospital and making sure enough food and supplies are all in place.

The county has already woken up to frosty mornings over the past few days but colder air coming in from the east could see smatterings of snow, rain and sleet, making the roads more hazardous.

Temperatures are expected to drop to between -2 and -3 degrees tomorrow night according to the Met Office.

During the daytime, the temperature is unlikely to rise much above freezing.

Police are warning drivers to take care on the roads and ensure windscreens are defrosted properly.

Ch Insp Di Roskilly from the Road Policing Unit said: "It sounds obvious, but there are still people who take risks with their own and others' safety by failing to defrost and demist their windscreens in the morning.

“If you are involved in a collision and the fact that you could not see where you were going is a contributory factor, you could be charged with either careless or dangerous driving. Cause a death and you could be looking at a prison sentence of up to 14 years.

"Leave sufficient time in the morning to defrost your windscreen and remain with your vehicle while you do so. Ensure that the screen wash is topped up and isn't frozen and that windscreen wipers and tyres are maintained in good condition. Officers will be conducting checks on vehicle condition as part of the current drink and drug driving campaign.

"Remember, drive carefully, slow down and take account of the icy conditions. Leave more time for your journey and ensure you leave enough space between you and the vehicle in front so that you can stop safely if you need to."

A spokesman for the AA said: “We have got more patrols lined up on the road and on stand-by. If people are looking to travel they should make sure they are properly prepared.”

West Sussex County Council said they were sending all of their gritters out last night to cover every major route. A spokeswoman added: “We will be constantly monitoring the situation.”

Conditions are expected to worsen throughout the week as Met Office predicts snow showers and ice on Friday.

A spokesman said: “On Friday the showers which were further north and east might drift across to the southern counties. There is an advisory for snow showers pushing their way across.”

Health bosses have said they are already being hit by the first waves of winter sickness.

The Royal Sussex County Hospital, Brighton, is experiencing its first outbreak of a highly infectious sickness and diarrhoea bug.

Sixteen elderly patients and one member of staff on Vallance ward have been struck down by the virus in the past few days.

The hospital has been forced to stop admitting patients onto the ward until all traces of the virus have gone.