Heavy snow has caused traffic problems and led to widespread school closures.
A Met Office yellow "be aware" warning said up to 8in (20cm) of snow could fall in some areas between 00:05 GMT on Friday and 18:00 on Saturday.
Nearly 200 schools were closed and several major roads were affected, with delays continuing into Friday evening.
The A55 in Denbighshire was closed for a few hours after several accidents and highways officals warned of "hazardous" driving conditions into the weekend.
Motorists have been warned to expect more delays as snow showers continue as there has been an amber warning issued for heavy snow on Sunday when some rural communities could be cut off.
The A55 reopened by 16:00 but sections just east of St Asaph were said to be particularly treacherous.
There was queuing traffic due on the A494 near the B5429 at Llanbedr Dyffryn Clwyd and the A465 between Tredegar and Brynmawr in Blaenau Gwent.
Drivers were also warned about conditions on the A5 at Chirk, Wrexham and a stretch of the A483 between Newtown and Welshpool in Powys was described as "treacherous" by police.
Dyfed-Powys Police asked for the road to be re-gritted but advised motorists to avoid the road unless their journey was essential.
Wrexham council said gritters would be out from 15:00 and would run continuously for 24 hours.
The Red Cross said its emergency response volunteers had been helping Betsi Cadwaladr University Health Board by transporting staff, equipment and blood supplies to hospitals.
Emergency response operations manager for Wales, Rob Donovan said: "We were asked by the health board on Friday morning to offer support and we have been assisting them in a number of ways throughout the day.
"The work we have done is in line with a long-standing arrangement with Betsi Cadwaladr Health Board whereby the Red Cross supports health professionals in north Wales during periods of adverse weather."
Interruption of power supplies in some rural areas is also possible.
Western Power Distribution, covering mid, west and south Wales, said the public can access their power cut map online.
Scottish Power customers across north Wales can check supply status in their postcode checker.
Cardiff Airport is not expecting disruption but they have warned passengers to keep an eye on their live flight information.
Welsh Water warned customers their pipes could freeze or burst when temperatures fall, costing thousands of pounds worth of damage.
It is offering free lagging kits - warm coverings around the outside of exposed pipes - to customers to protect pipe work.
Denbighshire council said it was prepared for the wintry weather with salt stocks at its three depots and its highways team geared up to work around the clock to keep the main A and B roads and roads connecting villages open.
Conwy council said it was "well prepared for winter weather", with 11,000 tonnes of rocksalt in stock and a fleet of 13 gritting lorries working out of three depots.
Gwynedd council said whenever snow or ice was predicted priority routes were pre-treated with salt and grit.