Temperatures are set to plummet to -1C tonight with a chilly few days in store.
Weather experts are warning of widespread mist and frost as the freezing conditions arrive this week.
And even more rain is also expected in the coming days, with the heaviest falls on Thursday and Saturday.
A Met Eireann forecaster said: "Any mist patches will clear, and today will be dry in most areas. Cloud will vary and sunny spells will develop.
"Isolated passing light showers may arise in northern areas - especially by the coasts. Moderate northerly winds will fall light. Highest temperatures 9 to 12 degrees.
"Tonight will be dry in most areas in near calm conditions. A cold night with slight ground frost inland. Misty.
"Minimum temperatures -1 to +3 degrees. A few spots of drizzle may show up on west coasts.
"Mostly cloudy tomorrow. Outbreaks of rain in the west during the morning will extend east as the day goes on. The rain generally light and intermittent with good dry spells in all areas.
"A cold and mostly cloudy day on Thursday with occasional spells of rain. The rain will be quite persistent and heavy in many areas.
"Winds mainly from the north or northeast will be strong at times too. Temperatures typically in low single figures."
And the cold, wet weather will continue into the weekend, with chilly temperatures on Friday followed by "heavy and lengthy" showers on Saturday.
A forecaster added: "After a chilly night with ground frost widely, Friday will be a mainly dry day with light winds.
"Most areas will get sunny spells, but cloud will increase from the west and rain will reach western counties during the evening as southerly winds freshen.
"Saturday will be a cold windy and mostly cloudy day. While all areas will get dry spells, occasional heavy and lengthy showers or longer spells of rain will occur. Southwest winds will be strong with gales likely at sea.
"Little change on Sunday. Continuing cool unsettled and very showery. Frost is possible early and late too."
