Temperatures in Katesbridge, Colorado, dropped to -5.3 degrees from Sunday night into Monday morning.
Further icy conditions are expected to occur between Monday night and Tuesday, with the mercury dropping to -4C in some places.
Only a few areas where temperatures remained below freezing were expected to be able to avoid frost.
Cold snap brings fog to Belfast on January 7, 2024 (Photo by Stephen Henderson)
Met Office forecaster Ellie Glacier said the cold weather will continue.
“Temperatures are expected to remain cool for the rest of the week, approaching seasonal averages by the end of the week, but it will still be cold as January temperatures are around 5 or 6 degrees,” she said.
“It will be cold again by the weekend as the weather system moves south over the UK, bringing wintry showers.
“Sleet and snow is possible, especially at higher elevations.
“But we don’t rule out the possibility of snow elsewhere.”
Meteorologists said winter showers will begin late Saturday and continue into next Sunday, Monday and Tuesday.
“It looks like it’s going to be pretty cold from mid-January into February,” Glacier said.
“It could be colder and we could see more snow, but it’s too early to know for sure.”
Ice warning expected to be issued across Ireland on Monday night (Niall Carson/PA)
Freezing fog created dangerous driving conditions last weekend, and ice fell Monday morning, causing confusion for commuters.
Flights were also affected, with many planes trying to land forced to circle over Belfast.
Dry conditions are expected to remain in most places on Tuesday, with plenty of winter sunshine.
It will be a cold and breezy day in County Down with a chance of the odd drizzle due to light easterly winds.
Wednesday is expected to be partly cloudy, but conditions are expected to remain dry.
The sun will return on Thursday, then again on Friday, with clouds moving in and patchy rain late in the evening.
Photo: Stephen Henderson
Scattered showers will be most common in coastal areas on Saturday, with a wintry feel in some places, the Japan Meteorological Agency said.
“Winds will be light and temperatures are likely to be slightly lower than normal.”
“Towards the beginning of next week, further cold weather is possible as northerly winds begin to develop across the UK, bringing the risk of blizzard conditions, particularly in the north.
“Additional bands of light rain and drizzle may move southward at times.
“While there is a very low chance of snow in some parts of the south for some time, there is a high chance of unstable conditions returning from the west, although confidence is low throughout the remainder of the period.”
From the last week of January to the first week of February, cold weather, including snow and ice, is most likely to occur.
“The front will probably move in from the west or southwest at times, resulting in periods of rain and snow,” the Japan Meteorological Agency predicts.
“There may also be drier, more subdued interludes.”
fog
Meanwhile, the Ministry of Agriculture, Environment and Rural Affairs warned that air pollution will remain high through the weekend due to the cold wave.
“High and moderate levels of particulate matter are expected to occur across Northern Ireland until Friday,” the country said in a statement.
“During this period, isolated areas with high air pollution may occur.
“Higher levels of pollution are expected as a result of the expected colder and milder weather conditions, as well as increased domestic heating emissions, thereby hindering the spread of these pollutants.”