Dozens of schools were closed and thousands of homes were without water as the UK continues to suffer from the effects of freezing weather.
Motorists have been urged to take care after temperatures plunged to -12C (10.4F) overnight, on the coldest night so far of the past week's cold snap.
Sub-zero temperatures in Dorset have frozen a half-mile stretch of sea.
The water supply to 5,000 homes and businesses in the Rhondda valley, south Wales, was restored on Wednesday night.
Welsh Water said around 400 homes in the Rhondda Fach valley remained cut off but their supply would be "back on soon".
Bottled water had been sent to the area, for the elderly, mothers with young children and those with special needs, after freezing weather damaged pipes to a treatment works.
The sea at Sandbanks in Dorset is partially frozen
Schools in Wales and Cumbria, which has seen snow, have been closed.
The current freezing conditions, caused by Arctic air sweeping across Scandinavia and over the North Sea, are set to last into the weekend.
Wednesday's overnight low was recorded at Benson, in Oxfordshire.
Daytime temperatures reached 2C (35.6F) to 3C (37.4F) across the UK.
In Sandbanks, in Dorset, the sea partially froze, the first time it has happened on the South Coast since 1991.
Freezing scenes from across the UK
BBC Weather presenter Nina Ridge said patchy mist and fog and a frost will form again overnight but it will not be as harsh or widespread as recently because of cloud cover.
Night time temperature averages are forecast to fall to about -1C (30.2F) in England, Wales and Northern Ireland.
The Met Office has advised local authorities across the UK to grit untreated roads, but said it would not be as icy as previous nights.
Scotland will see the first signs of the milder air moving in across Britain in the days to come. Overnight lows in the Northern and Western Isles are forecast to range between 3C (37.4) and 5C (41F).
The weather has resulted in the unusual sight of the fountains in London's Trafalgar Square fountains being frozen over.
About 30 schools closed for the day in Cumbria, which saw up to 7.6cm (3in) of snow overnight, and 15 remained shut in parts of north, west and south Wales.
The 50-pupil Ysgol Rhewl in Ruthin, North Wales closed after thieves stole the oil needed to heat its buildings.
The AA and RAC said they had dealt with an estimated 50,000 call-outs over the past two days.
Greater Manchester Police has also issued a warning to motorists to take care when defrosting their vehicles.
The force said 30 cars had been stolen since the start of the year - six on Wednesday morning alone - when drivers had left the keys in the ignition while defrosting them.
Ch Insp Haydn Roberts said: "People can be tempted to leave their car engine running on a frosty morning while they keep nice and warm inside their house."
In December, 46-year-old Caroline Johnson was scraping ice off her car in Slough, Berkshire, when a man jumped in. He ran her over as he drove off, leaving her with serious injuries.
Meanwhile, nature conservation groups, including the RSPB and the British Trust for Ornithology, have urged people visiting wetlands and the coast not to disturb water birds as it could threaten their survival in the cold weather.
But temperatures are still a long way off the record low of -27C (-16.6F) in northern Scotland 14 years ago.
Council leaders have warned that tens of thousands of pensioners could die as a result of the prolonged cold snap.
The Local Government Association said the number of deaths caused by the winter chill might exceed last year's figure of 25,000.
Its comments came as millions of pensioners and vulnerable people around the UK become eligible for cold weather payments.
The Department for Work and Pensions said cold weather payments had now been triggered at 52 weather stations around the UK since the start of this winter.
The payment, which goes to people in receipt of certain benefits - mainly pensioners, severely disabled people and families with a young or severely disabled child - rose this year from £8.50 to £25-a-week for each spell of cold weather.
It is paid automatically to those who qualify, including the estimated 2.7m households in receipt of pension credit.
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