A warning is in place of severe fog expected to blanket Cornwall this overnight tonight and into Friday morning.
The forecasters say fog is expected to become "widespread and locally dense again through Thursday night and Friday morning", with visibility likely to fall below 100 metres at times, locally less than 50 metres.
Adding that the public should be aware of the likelihood of difficult driving conditions and some travel disruption.
The Met Office's chief forecaster said: "Thursday morning's fog, having cleared inland, will have persisted through much of the day in some coastal locations and may begin to spread inland again quite early on Thursday evening.
However, across most inland areas fog patches will form more widely overnight into Friday morning.
"As was the case on Thursday, not everywhere in the yellow area will see fog, but where it does form it is likely to be dense. Fog will then slowly clear through the mid morning period."