Thermometers will widely nosedive from Wednesday amid warnings the United Kingdom will stay locked in the freezer until spring.
A blast of Arctic air will bring freezing temperatures to the United Kingdom this week and end what has been a mild start to the new year.
Snow could arrive in Northern Ireland as soon as this weekend..
But a spokesman on Tuesday said that while Britain being hit by a new Beast from the East could not be ruled out, the forecast so far suggests the country will see stable weather conditions.
Last week the Met Office said there was an "enhanced risk of snow" for Northern Ireland and the rest of United Kingdom towards the end of January and the beginning of February.
"Another front moves in from the north on Thursday introducing properly cold air to the country and this is when we expect much colder conditions across the UK".
Today, the county is under an amber code, meaning road surface temperatures could drop to as low as zero.
"Sunday night will bring a widespread frost to the north of the United Kingdom, with icy stretches possible".
But if we are going to get hit by snow, and it remains a big if, it is going to come at roughly the same time.
"It turns colder still on Friday with temperatures dropping to low to mid-single figures, there is something trying to push in from the Atlantic which although looks predominantly like rain, could bring some snow".
"We are looking at the next week or so, but we could see a change after that".
The Met Office's United Kingdom outlook for the next 30 days is: "It will be mostly settled for a time on Friday, especially in the east, before thickening cloud and outbreaks of rain, perhaps with some hill snow, try to move eastwards later, with strong winds".
A possibly lengthy winter blast will be driven by warming of the air over the North Pole encouraging a colder airflow into the UK.
"That has a tendency to lead to cold weather in Scotland but doesn't necessarily".
While this is the norm for January, Diamond said people will not be used to the cold after such a mild start to the year.
"Winter certainly looks like arriving with a vengeance before the weekend which now looks like the coldest since a year ago". However, the cold weather may not affect the whole of the United Kingdom and it is still possible that some milder and wetter interludes will intersperse this generally cold period, especially in the south.
"A lengthy cold and wintry spell could hold out well into the meteorological spring", he added.