As high pressure draws in and the weather settles down, we're more likely to start seeing some more seasonable features like fog.
Autumn and winter is the perfect time for fog to develop, especially in periods of high pressure dominated weather, with weaker winds allowing dense, stubborn fog to settle, even for days at a time.
This is because in the cooler months, under clear skies at night, heat from the ground can quickly escape allowing for the temperature to drop below the dew point.
In valleys, fog forms in clear, calm conditions. The cold air sinks downwards, allowing the air to cool beneath the dew point and condense.
There are several types of fog that form in different ways, including valley fog, radiation fog, advection fog. Sea fog, often a result of advection fog, is known as 'haar' or 'fret' in some parts of the UK. It is most common along North Sea coasts.
Because of the many factors involved, forecasting the arrival and exact location of fog is actually quite tricky. If just one aspect of the development is out of sync, fog is unlikely to form.
Cloud cover, wind speeds, temperature, moisture levels, and daylight hours all play a role.