Temperatures were expected to plummet as low as minus 10C (14F) tonight with the big freeze set to last well into the new year.
Snow showers and ice caused widespread disruption in the east of the country, with Dublin Bus services and flights into and out of Dublin Airport suspended for a time.
Met Éireann said snow showers would die out in Leinster followed by a frosty, icy night.
Forecaster John Eagleton said the icy temperatures would continue into next week.
“It looks like the weather is going to stay solidly cold for next week,” he said.
“Maybe the temperatures not dipping as low as they will tonight.
“We’re forecasting minus 5C (23F) to minus 10C (14F), and I think that’s a pretty good general description.”
Gardaí and the AA advised against driving in midland, western and eastern counties with frozen snow, slush and black ice causing dangerous driving conditions.
Heavy snow closed Dublin Airport for a time but it reopened mid- morning.
Bus Éireann was forced to cancel several services due to treacherous conditions, including Sligo and Ballina routes.
Met Éireann said tomorrow was expected to be cloudier than today, bringing with it snow flurries.
Temperatures were expected to remain around freezing.