Met Éireann has issued a yellow weather warning for the early hours of Monday morning.
The fog warning covers the entire Republic of Ireland and came into effect at 1am.
The notice will remain in place until 11am, with the forecaster warning that conditions may impact visibility.
Issuing the warning at lunchtime on Sunday, Met Éireann said: "Mist and fog will form again tonight, becoming dense, especially in some midland areas, leading to poor visibility."
— Met Éireann (@MetEireann) October 10, 2021
The fog is expected to clear around midday, leading to a dry and sunny day across the country.
It will remain bright in Munster through the afternoon, but cloud will build slightly elsewhere. Highest temperatures are due to be in the region of 12-15 degrees.