Autumn has begun and so has the season of fog. Here are some facts, tips and rules of thumb about fog.

In autumn, high-pressure areas can provide not only a beautiful Indian summer or a golden October as we will be experiencing this week, but also stubborn fog in some places.

Particularly in the winter months, the earth's surface cools down considerably on clear nights. The temperature drops until it reaches the dew point and condensation begins. The result: fog.

Clouds, on the other hand, act like a blanket and keep the heat on the ground. This inhibits the formation of fog.

On clear, calm nights conducive to the formation of fog, a temperature inversion takes place. The cold air subsides and drags down to the valleys, leaving the higher hill-tops and mountain-tops warmer. However, following normal physics in the troposphere, the lowest layer of the atmosphere, temperatures cool with altitude. Fog can then form in the valley bottoms, remaining stagnant until a breeze kicks it up and mixes the air around.

On the WeatherRadar it is easy to see which areas are affected by fog. If you are leaving for your early morning commute or perhaps a walk in the hills, you can ensure that the destination is outside or above the fog.

The shallower the cold air over a fog-filled lake is, the faster it can dissipate during the day. With a thicker layer of fog, a larger amount of the air must be heated until the fog disappears.

If sunlight falls on the water droplets of the fog, mysterious optical phenomena, such as Glories or Brocken Spectres can occur. How this works exactly, you can read in the weather lexicon.

In addition, in winter, fog and wind can create magical works of art called rime.

Wind can also dissolve the fog, or prevent its formation. A light wind is enough to kick up the cold surface air, and mix it with warmer air from above.

The areas most often plagued by fog are in river valleys and on lake shores. Especially in autumn, a lot of moisture evaporates from the still, warm waters, conducive for the formation of fog.

On the coasts, a different process causes sea fog, especially in spring.

We've all experienced it at some point: although the sun was forecast, we were stuck in permanent grey all day. Fog forecasts are among the most difficult predictions. The weather models are often off the mark, especially when it comes to the time of dissipation. In general, the later in the fall, the greater the chance of it remaining stubborn all day.

Especially in winter, when there is a lot of heating, pollutants collect in the air near the ground. Because of the inversion, there is hardly any exchange and mixing of the air. Fine dust pollution then not only increases for us it also increases the formation of fog as water vapor condenses on the fine soot particles.

Autumn fog is among the most beautiful weather features to photograph. The perspective from mountains or hills on the sea of fog also makes for enchanting pictures.