A seven-hour weather warning for three counties has been issued as snow looks set to hit certain areas.
The Status Yellow ice and snow alert is in place for Donegal, Leitrim and Sligo from 3am until 10am on Friday.
Met Eireann warns that some icy stretches are expected in these counties.
Before then, Thursday will be mostly dry for daylight hours across Ireland, outside of patchy drizzle, mainly across the midlands and southwest, with the best of any sunny spells across the east.
However, later in the afternoon, a band of heavy thundery rain will move into the northwest and west, sinking down into other areas later.
It will also become windier through the day, as southwest winds increase fresh to strong and gusty at times, and veering northwesterly with the passage of the rain, while it will be mild with highest temperatures of 10 to 12C.
Met Eireann predicts that hail sleet and snow will hit the northwest of the country overnight on Thursday.
A forecaster said: "The band of heavy and persistent rain will clear southeastwards early tonight, followed by cold and clear conditions with frost and possible ice setting in.
"Windy at first, but west to northwest winds will moderate away from the west and north coast. Scattered showers will feed in later, mainly into Ulster and Connacht, some of hail and sleet, with snowfall mainly over higher ground.
"A few isolated thunderstorms are likely too in northern parts. Lowest temperatures of -1 to 3C, coldest away from the west coast.
"Friday will be a cold, bright day with sunshine and showers, some heavy and of hail and sleet too for a time; with the showers most widespread in northern parts.
"Some snow showers are likely too for a time in Ulster, especially over higher ground. Later in the day the showers will become more isolated and will mainly be of rain, though still some wintry showers in northern parts.
"Highest temperatures of just 4 to 8C and feeling colder in moderate to fresh and occasionally gusty westerly winds."
Looking towards the weekend, they added: "Cold with a scattering of showers early on Friday night, mainly in western and northern parts, some still wintry in the north, but the showers will soon die away.
"Lowest temperatures of 0 to 4C early in the night with winds generally easing and with some frost and ice forming away from western and northwestern coastal parts.
"It will become less cold though from the west overnight though as cloud increases from the west and with southwest winds freshening a little. Outbreaks of rain and drizzle will move into northern and western parts of Ulster later in the night.
"Saturday will be a mostly cloudy, breezy day and it will be mainly dry to begin in most places.
"Rain and drizzle will push down from the northwest over much of the rest of Ulster and Connacht too through the morning, extending further southwards through the afternoon and evening, though much of south Leinster and south Munster will hold dry. The rain will be heavy at times in Ulster and parts of Connacht too.
"Becoming milder with highest temperatures of 8 to 11C in mostly fresh and gusty southwest to west winds, stronger in northwestern and western coastal parts.
"Cloudy on Saturday night; with outbreaks of rain in many parts, with some heavier bursts at times. Continuing breezy in moderate to fresh southwest winds. Lowest temperatures of 4C in the north to 8C in the south.
"Continuing mostly cloudy on Sunday with outbreaks of rain and drizzle, most persistent and widespread early in the day, but good dry spells developing later. Mild with highest temperatures of 9 to 12C in moderate to fresh and occasionally gusty westerly winds, stronger in western coastal parts."
