The warning is for counties Cavan Donegal and Monaghan as well as all of Connacht
It will be in effect from 10pm until 10am.
The forecaster has warned of poor visibility and difficult travelling conditions over the course of the 12-hour period.
Tonight will also be quite cold with lows of between -1C and 4C in places.
There will be some frost, with eastern and southern coastal areas seeing the warmest of the weather.
Tomorrow morning will start cold, with any frost clearing early on, but the mist and fog will gradually clear through the morning and will possibly linger in some areas into the afternoon.
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