The UK weather worsened as freezing fog and ice covered the entire country leading to travel disruptions as flights were grounded at Heathrow Airport and London City Airport, with further cancellations and delays expected through the day.

The Met Office has issued a yellow warning for fog in parts of England and has warned people of reduced visibility and risk of travel disruption, which was seen earlier as well when snow hit the UK. Visibility will be less than 100 metres in worst affected areas, said the Met Office.

More than 20 flights due to take off on Wednesday were cancelled at the Heathrow Airport. 18 flights were cancelled at London City Airport. The Met Office weather warning, which covers a period until 11:00 GMT today, warns of dense and freezing fog across much of central, eastern and north-west England, as well as London.

Passengers at London’s Heathrow Airport have been advised to contact airlines to check details. Cancelled flights include trips to Warsaw, Nice, Stockholm, Aberdeen and several German cities. After experiencing the coldest night of the year on Monday, when temperatures fell as low as minus 10C (14F), most parts of the country is expected to suffer sub-zero temperatures today as well.

Weather forecasters say that central England, Wales and East Anglia, which have already been hit by fog, are expected to experience worse weather today. Rain and snow on higher ground is expected, milder weather is expected later in the week, but rain could lead to local flooding on Friday.

Julian Mayes, forecaster for MeteoGroup, 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.”, Mayes said.