Experts are warning of travel disruption, including cancelled flights, as severe fog is forecast to hit much of the UK on Tuesday.
The extreme conditions are expected to last until midday on Tuesday, with some patches of freezing fog overnight.
The Met Office said: "Fog is expected to form widely across southern and central England and some eastern parts of Wales on Monday evening, persisting overnight into Tuesday.
"Slower journey times are likely with delays possible to bus and train services. Some delays or cancellations to flights are also possible."
It added that with light winds and clear skies expected to form quite widely on Monday night, visibility could fall below 100m in some places.
Only a slow improvement in conditions is expected on Tuesday morning.
A yellow weather warning is in place for the East Midlands, the East of England, London and the South East, North West England, South West England, Wales and the West Midlands.