A yellow weather warning is in place for Leinster, Munster, Connacht and counties Cavan and Monaghan with dense fog set to appear overnight.
The Met Éireann warning issued on Saturday morning includes 25 counties of the State, excluding only Donegal.
The UK’s Met Office has not issued a warning for the remaining six counties of Ulster.
The Met Éireann warning cautions that visibility will be poor and travel difficult in the areas affected.
RM Block
The warnings come into place from 9pm on Saturday and expire at 11am on Sunday, with the difficult weather potentially affecting some Sunday morning travel.
A yellow warning is issued when weather conditions are not especially unusual, but where danger exists in localised areas.
Saturday was expected to be clear in much of the country with only patchy outbreaks of rain and some lingering fog. Highs of 7 to 11 were expected, with light breezes.
These conditions are expected to give way to the widespread fog as the evening progresses. Lows may drop as far as one degree in places.
On Sunday morning, the fog will gradually lift, lingering in some places, with another cool day to follow amid highs of 7 to 11, and breezes strengthening into the night.
Wetter and breezier conditions are expected to take hold as the week progresses.
