Drivers are being warned to be on their guard as widespread freezing fog and icy conditions descend on the UK.
Large swathes of the country are expected to experience adverse weather after one of the coldest nights of the year so far.
On Monday night, the mercury plummeted to a chilly minus 10C (14F) in some parts of the country, with Scotland experiencing the lowest temperatures.
Julian Mayes, forecaster for MeteoGroup, the weather division of the Press Association, said central England, as well as Wales and East Anglia, had been hit by fog, which is likely to spread through the night.
He said: "The fog is currently pretty widespread. It's currently located over central England as a large area of low cloud, which is descending down as fog.
"Visibility is poor and the areas affected include the Midlands, the eastern side of Wales, most of East Anglia, most of the area just to the north of London, Bristol and parts of central southern England.
"Through the night it's going to return to Somerset and become a bit more widespread in valleys across Wales. The far south east might miss it, although the London suburbs may become affected later on tonight."
Mr Mayes said in the worst affected areas there will be less than 100 metres visibility.
The weather is expected to get even worse on Wednesday, with rain and snow predicted on higher ground.
"Tomorrow when the fog lifts the weather is going to become a little more unsettled for the second half of this week with rain," he said. "Probably no significant snow but it will end up wet and windy by Friday, so a big change is coming."