Snow has fallen across large parts of Wales making travel conditions treacherous in many places and closing hundreds of schools.
The Met Office has issued a severe weather warning, saying some areas could have up to 15cm (6in) of snow.
The snowfall brought disruption to bus and train services and the closure of Cardiff airport's runway.
Some roads have been closed and there have been warnings in many areas not to drive unless essential.
The worst affected areas have been the south Wales valleys, parts of Pembrokeshire and Ceredigion and the Brecon Beacons.
Forecasters said conditions were expected to improve in Pembrokeshire, Powys, Ceredigion and across much of south Wales during the morning, but snow was worsening in north Wales, persisting into the evening when ice was predicted to be a problem in many places.
But some southern and western areas of Wales, including parts of Pembrokeshire, Carmarthen Bay, Swansea and Gower have escaped the snow.
Malcolm Weatherall, from the Met Office in Cardiff, said conditions would worsen in north Wales during the day.
He said: "The southern half of the country has probably been worst hit.
"Some areas escaped it, places like Milford Haven, southern parts of Pembrokeshire and Carmarthen Bay - I think they had sleet rather than snow.
"The improvement will come from the south. For mid Wales, I think we're going to have to wait until lunchtime for that improvement.
"For north Wales, it continues snowing on and off through the afternoon and into the evening.
"As we go through the day conditions will deteriorate inn parts of Powys, Ceredigion and parts of north Wales north Wales.
"So worse to come for that northern half as we go through the morning and afternoon."
The A55 near Conwy was said to be dangerous with speed restrictions at the Britannia Bridge.
Gwent and South Wales Police were using 4x4 vehicles rather than normal patrol cars and there was snow throughout Powys, with deeper accumulations on higher ground.
Gwent Police said the Caerphilly area was the worst affected in their force area, but most major roads were passable.
The Dyfed-Powys force said most roads were treacherous but most passable with care.
Rhondda Cynon Taf Council closed three mountain roads, Maerdy, Bwlch and Rhigos, at 2100 GMT on Wednesday in anticipation of the heavy snowfall and South Wales Police shut the A4107 between Abergwynfi and Treorchy for the same reason.
In Ceredigion, the A44 in Lovesgrove near Aberystwyth is closed with the same road also closed at Llangurig in Powys.
The A4226 Port Road in Barry is also closed because of the snow.
Rail disruption
Drivers were warned to take extra care and motoring organisations advised people travelling by car to take warm clothes, food, water, a torch and a spade in case of a breakdown.
Train disruption was expected and there were numerous flight delays and cancellations at Cardiff International Airport, where the runway was closed.
All flights there have been delayed, but the airport was asking passengers to turn up as normal.
Arriva Trains Wales said it had allocated extra train and staff resources but warned passengers to allow extra time for their journeys.
Virgin Trains said most of its north Wales services would not operate south of Crewe, where passengers will need to change for alternative trains.
Stagecoach Coaches said no services were running out of Merthyr, Aberdare, Brecon, Caerphilly or Porth with local services cancelled in Brynmawr and Cwmbran.
School Closures in Torfaen Include:
Hillside Primary School
West Mon School, Pontypool
Pontymoile Primary School
Trevethin Community School, Pontypool
Hillside Primary School, Blaenavon
Fairwater Juniors and Infants School, Cwmbran
Ysgol Bryn Onen, Pontypool
Ysgol Gymraeg, Cwmbran
Ysgol Bryn Onnen, Pontypool
Maendy Primary School
New Inn Primary School, Pontypool
Blaenavon Hillside Nursery
Coed Eva Infants and Juniors
Abersychan School
Ysgol Gyfun Gwynllyw
Penygarn nursery infants and juniors, Pontypool
First published on BBC Wales website|