The icy weather is expected to impact much of the country from 9am on Wednesday (today) until about midnight on Thursday (tomorrow).
The police asked drivers to be prepared for possible travel disruption.
Chief Inspector Louise Blakelock, Road Policing, said: "There is a risk of localised disruption to travel likely throughout tomorrow and Thursday and we would ask motorists to take precautions before they set off.
"If you are travelling you should ensure that you and your vehicle are adequately prepared for the conditions. Make sure you have sufficient fuel and supplies such as warm clothing, food and water in the event you are delayed for several hours. Charge your mobile phone and plan your route as well as alternative routes.
"Road Policing crews will be patrolling the road network to keep people safe during this period - please follow our advice to travel with extra caution."
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