July, the mean temperature of Geneva is 20 °C, alongside the southern edge of the Jura it is 18 – 20 °C, and in higher regions 16 – 18 °C. With regard to mean sunshine duration, the Lake Geneva region is again advantaged with more than 1900 hours, whereas in the rest of the Swiss Plateau, it is between 1600 (especially in the east) and 1900 hours. The annual average rainfall is between 800 millimetres near the Jura, 1200 millimetres in the higher regions and 1400 millimetres at the edge of the Alps. The driest regions of the plateau are in the lee of the High Jura between Morges and Neuchâtel. In the warmest regions at the lakes of Geneva and Neuchâtel, there are less than 20 days with a snow cover, whereas, in the rest of the plateau, it is between 20 and 40, depending on the height. In the winter half-year, the air on the Swiss Plateau can stay still, with little exchange for the rest of the atmosphere, building a lake of cold air on the plateau and often a ceiling of high fog. The clouds look like an ocean of fog when seen from above, (usually around 800m) and hence are called the 'nebelmeer'. This weather is called inversion because the temperature below the fog is lower than the temperature above. Sometimes, it lasts for days or even for weeks, during which the neighbouring regions of the Alps and the Jura can have the brightest sunshine. Typical for the high fog is the bise, a cold wind from the northeast. Since it is channelled by the Swiss Plateau narrowing in the southwest, it reaches its major strength in the Lake Geneva region where wind speeds of 60 km/h with top speeds of more than 100 km/h are usual in typical bise weather. The regions near the Alps of the central and eastern plateau sometimes have temperature rises due to the warm foehn wind. The dominating vegetation in the Swiss Plateau is a mixed broadleaf forest with European beeches and silver firs. For forestry, there are major plantations of Norway spruces in many places, though the Norway spruce naturally only grows in the mountains. In certain favoured spots that are warmer and drier, in the Lake Geneva region, in the Seeland and in the northern plateau between the Aare orifice and Schaffhausen, the predominant trees are oak,