Met Éireann predicts that this morning's fog and frost will clear by the afternoon, with sunny spells and dry conditions expected.
The forecaster says winds will remain mostly light throughout the afternoon, with highest temperatures between 10 and 12 degrees.
AA Roadwatch warned of light frost on roads in Longford Town and Castlebar, while there is dense fog on the M1 and around Tralee and Drogheda. It advised motorists to use foglights were needed.
The fog is set to return to many areas again tonight, clearing from the northwest. Parts of Ulster and Connacht will see outbreaks of rain.
Overnight, temperatures in Leinster and Munster will dip to minus 1 to 1 degree, while Ulster and Connacht are in for a milder night of 2 to 5 degrees.
Tomorrow is predicted to be cloudy with some outbreaks of rain and highest temperatures of 10 to 13 degrees.
The weekend is predicted to be mainly dry.
