The Met Office had sent out a yellow warning yesterday, meaning social and healthcare services should prepare for a potential period of cold weather.
But today it was upgraded to amber, signalling a significant chance of severe cold weather.
It means there is an increased health risk for vulnerable patients and a chance of disruption to the delivery of services.
This level of warning also requires social and healthcare services to target specific actions at high-risk groups such as the very elderly and those with chronic diseases.
The Met Office said there was a 90 per cent chance of severe cold weather, icy conditions or heavy snow in the region from today until 9am on Saturday.
It said: "Colder conditions will spread in from the south later on Wednesday into Thursday, bringing with it sharp overnight frosts and suppressed temperatures by day.
"It may take until Saturday for less cold air to arrive from the west."
Advice issued with the warning added: "Prolonged periods of cold weather can be dangerous, especially for the very young, very old or those with chronic diseases."
Meanwhile, officials are directing people to NHS on protecting your health during very cold weather.
Click here to be taken to their advice.