The warning is in place until tomorrow morning.
Met Eireann has issued a status yellow fog warning for two midlands counties.
Dense fog is expected in Offaly and Westmeath from 10pm until 12 noon tomorrow.
The warning is also in place for Cavan, Monaghan, Connacht, Longford, Louth, Meath,
The forecaster also says we can expect spells of rain, which will be heavy at times, which may lead to localised flooding.