Lake Geneva °C in 53 years), while the average temperature of surface water (5 meters deep) increased from 10.9 °C in 1970 to 12.9 °C in 2016 (+ 2 °C in 46 years). Lake Geneva (and particularly the lakeside parts of the city of Geneva) can be affected by the cold Bise, a north easterly wind. This can lead to severe icing in winter. The strength of the Bise wind can be determined by the difference in air pressure (in hectopascal [hPa]) between Geneva and Güttingen in canton of Thurgau. Bise arises as soon as the air pressure in Güttingen is higher
Geneva 15.7%. Of the agricultural land, 0.3% is used for growing crops. Of the water in the municipality, 0.2% is composed of lakes and 2.9% is rivers and streams. The altitude of Geneva is , and corresponds to the altitude of the largest of the Pierres du Niton, two large rocks emerging from the lake which date from the last ice age. This rock was chosen by General Guillaume Henri Dufour as the reference point for surveying in Switzerland. The second main river of Geneva is the Arve, which flows into the Rhône just west of the city centre. Mont Blanc