Temperatures dropped to minus seven in parts this morning.
There was snow in parts of Kerry, Cork, Sligo and Donegal - with some schools in Donegal closed.
A weather advisory will remain in place until Friday.
Alan O'Reilly from Carlow Weather says it will warm up over the weekend:
"It's going to stay cold up until Friday, it looks like," Alan said.
"Wednesday night (tomorrow night), it'll be very very cold again."
Alan says it'll be cold tonight but with cloud and snow showers it won't be as bitter.
Friday afternoon will see things improve a bit, and the by Saturday temperatures will be back above ten degrees according to Alan.
A yellow snow/ice warning issued for Donegal and Leitrim now with some heavy snow showers likely today. pic.twitter.com/LhvGlmxn36
— Carlow Weather (@CarlowWeather) January 17, 2023
It Could Be Worse
If you thought it was cold here - temperatures in the town of Yakutsk in north east Russia have fallen to minus 50 celsius.
Less than a million people live there because it's exceptionally cold (even by Russian standards.)
One resident told Reuters the best way to battle the cold is to layer up, 'like a cabbage,' she said.
Summer (Could Be A) Scorcher
Global temperatures could hit record highs this year
There's expected to be an every seven year event called - El Nino which hasnt' happened since 2016.
Its a phenomenon involving warmer wind and sea currents across the Pacific Ocean.