Scores of schools in Wales will close again on Thursday because of expected heavy snow, as road salt supplies run low in some areas.
Powys council announced on Wednesday its 120 schools would shut the next day "to remove any uncertainty".
Some 60 other schools in Caerphilly, Rhondda Cynon Taf, Merthyr, Blaenau Gwent and Torfaen will also shut.
Meanwhile, Ceredigion and Rhondda Cynon Taf councils say their supplies of road salt are falling fast.
Powys council said following weather advice forecasting further significant snowfall across the county overnight, every school in Powys would be closed on Thursday.
Council spokesman Douglas Wilson said: "Decisions such as these are not taken lightly. We have taken this decision following the latest weather advice and to remove any uncertainty."
The council said schools were expected to re-open on Friday but that decision would be made on Thursday afternoon.
The NUT Cymru said head teachers had had to pay attention to severe weather conditions when deciding to shut their schools and had "little choice" to act otherwise.
As the freeze continued, Ceredigion council's highways' director told BBC News that the local authority had only four or five days supplies of road salt, and just two days' if there was heavy snow.
The council said had it decided to keep its salt stocks for use on primary and trunk routes and to react when needed on secondary routes after a supplier said it had no more available.
Rhondda Cynon Taf council said it had a "major concern" that its order for 600 tonnes of salt, plus orders by other local authorities, had been blocked for the supplies to be used on motorways and major trunk roads.
In response, a Welsh Assembly Government spokesperson said it had delivered 100 tonnes of salt to each of seven local authorities in south and mid Wales.
She said: "We are in constant communication with local authorities to see what needs to be done to keep stocks up to essential levels."
Rhondda Cynon Taf has also cancelled all home-to-school transport in the borough on Thursday, as it did on Wednesday, but said the decision on whether a school closed rested with the head teacher.
The local authority said its three mountain roads - Bwlch, Rhigos and Maerdy - will be closed from 2200 GMT on Wednesday.
The Welsh Local Government Association said: "Although we have seen stocks being drastically depleted over the last few days, the public can feel reassured that enough grit is still currently available."
The Met Office has issued an early warning of more sleet and snow for Wednesday night and Thursday, with south-east Wales and Powys expected to see most of the snow.
There could be about 2 - 5cm (0.8 - 2.5in) in general, with 5 - 10 cm (2 - 4in) likely in places and 20 - 30 cm (8 - 12in) possible over higher ground with bigger drifts.
Meanwhile, there were warnings for motorists on Wednesday to take care on the roads because of icy conditions.
On Wednesday, the A4061 Bwlch road and the Rhigos road were both closed during the day and the Maerdy mountain road was only passable with extreme care.
Many rural roads across south and west Wales were impassable because of ice.
Travel reporters said traffic levels on Tuesday had been down to Sunday levels as many people stayed at home because of road conditions or difficulties with childcare.
Emergency services and councils loaned 4x4 vehicles and drivers to hospitals in Swansea, Neath Port Talbot and Bridgend on Tuesday to ensure workers cut off by snow or hit by public transport cancellations were able to get to work.
On Friday, light snow in the south and east is expected to move away, and it is likely to brighten up with sunshine and a few wintry showers.
Met Office forecaster Derek Brockway advised any rugby fans planning to travel to Scotland for Wales' opening Six Nations game on Sunday to allow extra time for the journey.
He said it should be dry and bright for the match at Murrayfield on Sunday afternoon, but there was a risk of snow there by Sunday evening.
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