Motorists in the north have been warned by the AA to leave extra early if they have to go out on the roads overnight and especially tomorrow morning.
Heavy snow was forecast over but has started to fall in Belfast city centre from 10:50pm on Tuesday night.
Freezing temperatures are forecast overnight in the south but no snow is said to fall tonight. Temperatures are forecast to get slightly milder by the weekend but black ice will still be on the roads overnight and early morning.