The Arctic weather conditions have caused disruption to bus services in Londonderry.
The Lone Moor Road service has been suspended and most other services are running a limited or main road-only route.
The rural services to Park village and to Donemana have been suspended.
The 212 Derry to Belfast will operate a reduced service from 1300 GMT, with buses on the hour. There are minor delays on the Derry to Dublin service.
City of Derry Airport is currently closed with updates expected at lunchtime. Long delays are expected.
In Castlederg, County Tyrone, overnight temperatures plunged to -14C.