The yellow ‘be aware’ warning is from 7pm tonight until 10am tomorrow.
The chief forecaster said: “With largely clear skies and light winds, patchy fog will soon begin to form on Monday (October 31) evening and become widespread overnight into Tuesday morning with visibility down to 50-100m in places.
“The fog will progressively clear from the north early on Tuesday although some patches may persist well into the morning in the extreme south.”
This follows two warnings early last week for patchy fog.