Temperatures are expected to drop below freezing point on Saturday night, bringing widespread frost across the country, according to Met Éireann.
It comes after an extended warm spell in the last week of March, with temperatures having hit 20 degrees in some areas.
Lowest temperatures of -4 and +1 degrees are forecast over Saturday night, bringing mist and fog in places, though it is expected to be largely dry with light winds.
Before the cold of the night arrives, however, it is expected to be largely sunny nationwide on Saturday evening after showers throughout the day clear.
Met Éireann said on Saturday temperatures will return to average throughout next week with blustery, cloudy and overcast conditions, before brightening up slightly in the middle of the week.
Overall conditions will remain unsettled and wet.
Sunday
Cloud will increase towards Sunday morning from the northwest with some patchy drizzle developing in the west of the country, Met Éireann said.
Sunday will start cold with some frost and fog patches, though southern and eastern counties will experience a dry and sunny morning.
Cloud is expected to thicken in the north and west, and rain will develop there around noon. Over the afternoon and evening, the rain will extend southeastwards.
Highest temperatures on Sunday will reach between 9 and 12 degrees with west to southwest breezes, according to the national forecaster.
Sunday night is not expected to be as cold as Saturday, with lowest temperatures of 6 to 8 degrees.
Met Éireann said it will be a cloudy night, however, with outbreaks of rain and drizzle. The rain will be heaviest and most persistent in northern and northwestern counties.
Monday
Monday will be dull with scattered outbreaks of rain or drizzle, most persistent in the north and west.
It will be a breezy day with highest temperatures of 9 to 13 degrees, before turning mild and cloudy overnight with some more outbreaks of rain and drizzle.
Lowest temperatures on Monday night will reach between 6 and 9 degrees.
Tuesday
Tuesday will be another cloudy day, according to the forecaster, with rain likely in northern counties, and patchy light rain and drizzle elsewhere.
Highest temperatures of 10 to 14 degrees are expected, with some breezes and fresh west to southwest winds.
Overnight on Tuesday rain will extend across the country early, and will clear to showers later. Lowest temperatures on Tuesday night will reach between 4 and 8 degrees.