Parts of Ireland are to experience heat of up to 14C on Sunday afternoon, but it will be bitterly cold overnight with -2C temperatures.
Met Eireann is forecasting a "fine and sunny" start to the day.
Cloudy conditions in the north are to spread southwards by the afternoon. Top temperatures will range between 9C and 14C.
A spokesperson said: "Fine and sunny in many places to begin today, but cloudier conditions in Ulster will extend southwards to affect other parts of the country by the afternoon.
"Dry, apart from isolated light showers in Ulster. Maximum temperatures will range from 9 degrees in the north to 14 degrees in the southwest. Winds will be light northwest or variable in direction."
Large areas of the country will be hit with frost on Sunday night, as temperatures look set to plunge to as low as -2C.
A spokesperson added: "Tonight will be dry, apart from a few light showers in Ulster, with variable cloud amounts and clear spells.
"Minimum temperatures of minus 2 to plus 2 degrees with a grass frost forming in the near calm conditions."
Monday will be slightly cooler, with highest temperatures to range from 9C to 13C on what will be a cloudier day.
"Cloudier overall tomorrow, Monday, with the best of the hazy sunshine through the morning.
"A band of showery rain will sink slowly southwards over Ulster during the day.
"Staying mainly dry elsewhere, however, a few isolated showers may occur towards evening. Top temperatures just 9 to 13 degrees in light variable breezes."
