With temperatures set to tumble below freezing overnight, Heathrow airport's official Twitter account has tweeted:
Freezing fog is forecast for tomorrow morning. Check your flight status with your airline if you’re flying: http://t.co/Q8Iu72j9
There may be some disruptions tomorrow morning due to freezing fog tonight and tomorrow. Please check your flight status with your airline.
Clear skies and light winds are a recipe for fog to develop, so allow extra time to defrost your car and check before you travel.
It's another bitterly cold day today. It's all down to where the air originates from - and today's can be traced back to Russia.