Met Eireann are warning motorists to be wary of black ice and "dangerous conditions" on roads after a freezing night.
The national forecaster said that temperatures are unlikely to get above 5C in many parts of the country all day.
The cold conditions have already led to a number of bad crashes nationwide.
The forecaster tweeted this morning: "Icy stretches this morning & some lingering fog patches leading to dangerous driving conditions.
"Sunny spells will develop through the day with scattered showers affecting Ulster & eastern coasts. Cold with highs of just 1 to 5°C in light to moderate north to northwesterly winds."
And the cold weather is here to stay for the next few days although it could warm up as we approach the weekend.
Thursday could see temperatures as high as 10C during the day.
However, before that there will be a number of nights with temperatures as low as -2C.
The forecaster said: "Icy stretches this morning and some lingering fog patches leading to dangerous driving conditions in some areas. Brightening up through the day as the fog slowly lifts with sunny spells developing. Scattered showers will develop over Ulster and along eastern coasts. Cold with afternoon highs of just 1 to 5 degrees, coolest where fog lingers. Light northerly breeze becoming light to moderate northwesterly later.
"Scattered showers over Ulster and western coastal counties will continue and some may extend inland become wintry over higher ground. A moderate, occasionally fresh northwest to north wind will develop and temperatures will fall to be between - 2 and + 2 degrees. Frost and icy patches will form with any clear spells, however temperatures will increase through the night in the north of the country where cloud will build.
"Breezy tomorrow with scattered showers through the morning, most frequent in Ulster but becoming largely dry for most of the country by the afternoon. Moderate to fresh northwest winds with temperatures of 5 to 8 degrees in the afternoon.
"Rain will continue to affect parts of Ulster overnight but it will be mainly dry elsewhere with clear spells. Cloud will thicken in the west towards dawn. Lowest temperatures of -1 to +3, coldest in the east with patches of frost. Light easterly breezes."
