A yellow (be aware) warning for snow and ice in Northern Ireland has been issued by the Met Office.
Snow has been falling in some areas, including Armagh, Ballymena, Ballymoney and Draperstown.
A number of roads have been affected - a number of crashes have been reported on the Mountain Road between Coleraine and Limavady, while the Glenshane Pass has also been badly affected.
It is expected to get milder during the afternoon.
However, strong winds will increase further on Monday night with gusts of 60-70 mph possible especially towards the north coast.
Large waves may come on shore with a risk of coastal flooding.
BBC NI weather presenter Cecilia Daly said: "Colder weather returned on Sunday night with the showers turning increasingly wintry and some snow settled on the hills overnight.
"Five hundred feet is a good approximation for where snow will accumulate but occasionally hail, sleet and snow showers will reach low levels and icy conditions are likely through Monday morning's commute."