With no wind to disperse the low cloud, mist and fog and less sunlight to burn it off, anticyclonic gloom can set in
In summer, a high-pressure system over the UK usually means fine weather. But in the colder months it can result in anticyclonic gloom, characterised by grey skies, mist, fog and drizzle.
A settled high-pressure system brings stable conditions and impedes the usual vertical movement of air. This is a recipe for sunshine when humidity is low, but can act like a lid, trapping atmospheric moisture near the surface.