Temperatures are influenced by the lake (which engenders relatively mild Winters and nights). Thanks to its gradient and south-west orientation, Lavaux is partly protected from the northern winds and benefits from a lot of sunlight.
The annual average temperature reaches 10.5° Celsius ranging from 2° in January to 20° in July. In January, towards the end of the nights, the average temperature can fall to almost 0° C whereas at dawn in July temperatures can reach 16°. During the afternoon at the hottest moment of the day, January’s temperatures average 5° whereas in July, averages soar to 25°.
Direction of the Ideal Slope
Rain falls throughout the year and never has Lavaux gone a complete month without rain. It is dryer between October and April (80mm average) and in the Summer, around 110mm per month of rain falls. On the terraces, the slopes offer an ideal orientation to benefit from the sun and so the rays are stronger reaching over 50% from June to September. The walls of the vineyard terraces allow the average temperatures to be higher than averages throughout the year. The stone retains the heat during the day and releases it at night. Crucially, the walls absorb the sun’s energy and reflect it straight in front and provide protection against the North wind known as the “Bise”.
Global warming could have positive effects for the Lavaux vineyards during the next few years. It could help to diversify of types of vines and could lead to greater sustainability of viticulture in the area.
Source : REBETEZ, Martine, « Climatologie », in Lavaux, Vignoble en terrasses face au lac et aux Alpes, Lavaux World Heritage Site Application File for UNESCO, Cully, January 2006, pp. 49-52.