The warnings cover from 7pm this evening, Friday, through to 11am Saturday and again from 7pm Saturday until 11am on Sunday
The Met Office says
'Fog or freezing fog likely to lead to some travel disruption Friday night and Saturday.'
What to expect
Slower journey times with delays to bus and train services possible
There is a chance of delays or cancellations to flights
The Met Office defines fog as essentially a cloud at ground level that causes a reduction in visibility to less than 1000 metres.
It becomes a much more noticeable thick fog when the visibility drops below 180 m, while severe disruption to transport occurs when the visibility falls below 50 m over a wide area (referred to as dense fog)
What causes fog? Fog is caused by tiny water droplets suspended in the air. The thickest fogs tend to occur in industrial areas where there are more pollution particles in the air allowing water droplets to coalesce and grow
What is freezing fog?
Freezing fog forms in the same way as normal fog when the land cools overnight under clear skies. If there are clear skies, the heat radiates back into space leading to cooling at the earth's surface. This results in a reduction of the air's ability to hold moisture which