Met Éireann says there are hazardous conditions nationally, with a status yellow ice warning now in place.
It will run until midday, with black ice possible, as well as freezing rain.
A status yellow low temperature and ice warning comes into effect at 10pm tonight and will remain in place until 10am tomorrow, with temperatures set to drop to -4 over night.
The Road Safety Authority is advising motorists to slow down.
Charlie Weston of the Irish Independent says cold snaps are bad for your pocket given energy prices.
"With those October increase, you're probably talking about electricity and gas prices doubling in the past year.
"Home heating oil is up about 50% in the last year alone, even though it's come back a bit in the last while.
"Trying to get logs for the stove and the fire, they've gone very dear as well, up 30-40% and they're hard to get."