Part of the Merseyside coast has been experiencing its lowest temperature since records began.
A Met Office weather observing station on the coast at Crosby, north of Liverpool, recorded a temperature of -17C on Saturday night.
It was the lowest since operations began at the site in 1983
The low temperature caused a huge amount of sea smoke - or fog - to form on the surface of the water, reducing visibility, the coastguard said.
Sea smoke is a type of fog which commonly forms when very cold air drifts across relatively warm water.
A spokesman for the Maritime and Coastguard Agency (MCA) said the thermometer at its Liverpool Maritime Rescue Co-Ordination Centre (MRCC) read -17.5C.
The Met Office spokesman described the record low as a "truly exceptional figure given its maritime location".
"Temperatures below -10C may occur again tonight although the possibility of freezing fog patches may prevent values falling as low as what we have just witnessed," he added.
The Met Office said the region would experience a relatively sunny but cold day, with temperatures unlikely to rise above -1C.
It warned that widespread ice would form on untreated surfaces producing dangerous driving conditions and advised the public to take extra care on the roads.
A severe weather warning has been issued about potential widespread icy roads in Cheshire, Halton, Merseyside and Warrington.
Merseytravel, which oversees trains, buses and the Mersey Ferries, was not expecting any major weather-related disruption on Sunday.
Liverpool John Lennon Airport warned that some disruption to flight was possible because of adverse weather and cancellations at other UK and European airports.
Passengers are advised to check with their airline before travelling.