Dozens of flights were suspended in the UK and some schools had to close on Wednesday as snow blanketed much of the country.
Britain's national weather forecaster, the Met Office, said temperatures in the Scottish Highlands dropped to minus 15.4 degrees Celsius (4 Fahrenheit) overnight, the coldest night recorded this year so far.
Freezing Arctic air is expected to blast the UK for the rest of the week, it added, warning of travel disruptions and power cuts in rural regions in the north.
Bristol Airport in southwest England was temporarily closed for snow clearing and all flights were suspended on Wednesday morning. In London, Gatwick Airport said some passengers experienced minor delays.
In Wales, dozens of schools were closed amid heavy snowfall.
The Met Office said the unsettled weather was a result of a clash between an Arctic maritime air mass and milder Atlantic air. Sleet, snow and freezing temperatures will continue to affect most areas of the UK until Friday, it said.