FOG is expected to create some hazardous driving conditions on Somerset's roads tonight (October 22).
The Met Office has issued a severe weather warning for the county, urging motorists to take extra care with low visibility on many roads.
Visibility over the hilly areas of Somerset, including Exmoor and the Blackdown Hills, is expected to be reduced to around 50 metres.
In other parts of the region, visibility will fall to between 100 and 300 metres.
Mike Rigby, head of climate consultancy Original Carbon, said the fog is being caused by the movement of a warm, moist mass of air moving up from the south.
He said: “Once the fog clears this air mass may briefly give rise to some unusually high temperatures, as much as 18C before the temperatures plummet on Friday/Saturday, as cold air floods down from the Arctic."
The Met Office's yellow alert will be in place from 6pm tonight until 11am tomorrow morning.