Meteorologists warned on Friday afternoon that an icy night lay ahead for residents of Londonderry and Donegal.
The Met Office said: “Temperatures will fall sharply after dark on Friday evening allowing icy patches to form on untreated surfaces, including footpaths and cycleways.
“Some freezing fog patches are also likely overnight, most likely over eastern parts of Northern Ireland. Please be aware of the potential for difficult travel conditions.
“Clear skies will allow temperatures to fall widely below freezing on Friday evening.
“Particularly at risk of icy patches are roads, pavements and cycleways which are either still snow covered, where surfaces are wet from partially melted snow or standing water and areas where wintry showers occur after dark.”
Met Éireann, meanwhile, said: “Wintry showers will continue, mainly over the northern half of Ulster this afternoon, becoming confined to coasts by evening. Highest temperatures reaching only 4 to 6 degrees in light to moderate westerly winds.
“It will become very cold soon after dark as a widespread severe frost develops. Temperatures will dip to between -2 and -5 overnight with freezing fog patches forming in some areas in calm conditions.”