Met Office warning as snow falls in parts of Wales
Hazardous driving conditions are affecting roads in north and south Wales due to snow and ice.
The eastbound A55 was closed briefly at Rhuallt Hill in Denbighshire with reports of long queues.
Difficult conditions were reported on parts of the Heads of the Valleys road in Merthyr Tydfil.
The Met Office has issued a medium risk warning of blizzard conditions later on Friday in the Brecon Beacons while snow hit other parts of Wales overnight.
There are also reports of snow across Wales in Pontypridd and Aberystwyth as well as Dolgellau and Anglesey.
Council leaders said beforehand that they were well prepared to deal with the conditions, with some doubling salt stocks.
Environment Agency Wales warned of the risk of localised surface water flooding later in south Wales.
The Met Office says the south Wales valleys, the hills of mid Wales, the Black Mountains and the Brecon Beacons are likely to be worst hit on Friday.
It has been warning of over 10cm (4in) of snow on higher ground.
Traffic Wales reports "hazardous" driving conditions due to snow and ice are being reported in Merthyr Tydfil on the A465 Heads Of The Valleys Road around the A4060, the Dowlais roundabout and on the A470 around the A4102 Swansea Road.
Similar conditions are also reported on the A55 at Anglesey at J8 A5025 / Lon Pant, Llanfair PG.
Traffic Wales reported the A55 Rhuallt Hill has been partly closed due to stationary traffic, hazardous driving conditions and long delays eastbound between J27, A525 (St Asaph) and J29, Pant-Y-Dulath, because of snow.
Across Wales, councils said latest information about any school closures caused by the weather will be updated via their websites.
Flintshire council reported that Lixwm Primary School near Holywell had been closed with a partial closure at Ysgol Mornant primary, also near Holywell, for pupils living in upland areas.
And Denbighshire council said Tremerchion school has been closed because of the weather with bus services affected between Mold and Ruthin because of "traffic incidents" resulting from snow.
Local authorities and the Welsh government have been preparing all year for the wintry conditions by stocking bigger supplies of road salt than ever.
Councils have a target for salt stocks that is one-and-a-half times the average amount used over the last six winters.
Cardiff, Swansea, Caerphilly, Blaenau Gwent and Flintshire councils have at least doubled their stockpile. Others have hundreds of extra tonnes.
"We don't want to see Wales closed for business," said Steve Thomas, chief executive of the Welsh Local Government Association (WLGA) which represents councils.
"We have seen many councils double their supplies and we have also put in place a range of regional salt barns.
"What we want to try and do is make sure the road network is open," he told BBC Wales on Thursday.
South Wales Fire and Rescue Service said people should heed any advice as they received several calls to incidents last winter where people had been caught out in snow and icy conditions because they had not been prepared.
Acting chief fire officer Huw Jakeway said: "During periods of bad weather we would ask for people to be extra vigilant to ensure their safety and heed any advice given to stay indoors and avoid unnecessary journeys."
Dwr Cymru Welsh Water is advising people about potential problems caused by burst pipes which were a particular problem during freezing temperatures last December.
The company logged 5,000 calls from customers on Boxing Day alone, compared with 50 on a typical busy day, and about 185 during a cold snap.