The Met Office has weather warnings in place and travel is disrupted, but how unusual is this for the time of year?
Why is it so cold in the UK at the moment?
Cold air from the Arctic has been pushed over the UK. This has been caused by a high-pressure weather system over Greenland and Iceland moving eastwards towards another high-pressure system over Russia. The result is a cold air mass in between being squeezed southwards and over the UK. Weather warnings from the Met Office are currently in place for the northern UK until Thursday.
Is this weather unusual?
Not at this time of year. The Met Office chief meteorologist, Steve Willington, said: "Daytime temperatures [are] remaining only a few degrees above freezing in many places over the coming days and overnight temperatures dropping to -10C or lower in isolated spots. Although below average, these temperatures are not that unusual for this time of year."
The average daily temperature for December has ranged between 3C and 5C in recent decades and natural variability in weather means spells above and below the average. While the UK has been a little colder than average, southern Europe has been warmer than average.
The cold weather might feel surprising as it has followed a very warm autumn in the UK, the third warmest on record. "It changed quite quickly from that mild autumn, so it feels really cold," said Met Office spokesman Oli Claydon. "But there is nothing record-breaking or unusual about this cold snap at this time of year."
Is there any connection to climate change?
No. Climate scientists say "climate is what you expect, weather is what you get". Cold conditions are expected in winter, with the weather then varying above and below the average from week to week. For example, the first half of December in 2012 was even colder than now, but much milder weather in the second half of the month meant it ended up about average overall.
Does the cold weather suggest global heating may not be as serious as thought?
Of course not. It is just winter. The evidence that human-caused emissions of greenhouse gases are resulting in a dangerous heating of the atmosphere is unequivocal.
Prof Lizzie Kendon, a Met Office climate scientist, said: "As our climate warms our winters in the UK are becoming warmer on average which is already leading to a reduction in the number and severity of cold extremes we experience."
"This trend will continue under further global warming, but the UK can still expect to experience cold spells of weather, like we're seeing now, due to the natural variability of the British weather," she said. "Days below freezing, known as ice days, will still be possible in the future although they will be rarer."
It is in fact quite likely that 2022 will be the hottest year ever recorded in the UK. Mike Kendon, at the National Climate Information Centre, said: "Although it's too early to guarantee, the first 11 months of 2022 have set up the distinct possibility of a record-breaking warm year." Only an extremely cold December overall was likely to prevent a record, he said.
"All of the top 10 warmest years on record for the UK have occurred since 2002, a clear indicator of our warming climate," Kendon said. "Human-induced climate change has increased the likelihood of extreme heat as we saw in July this year, but this year has also seen persistent warmth resulting in the year overall challenging the record previously set in 2014."