In the second and third ten-day periods of April, and in some cases even over the first ten days of May 2017, western, central, southern and eastern Europe experienced a series of frosty nights, with catastrophic consequences in many places for fruit growing and viticulture. The worst-affected countries were Italy, France, Germany, Poland, Spain and Switzerland. Losses were so high because vegetation was already well advanced following an exceptionally warm spell of weather in March that continued into the early part of April.
For example, the average date of apple flowering in 2017 for Germany as a whole was 20 April, seven days earlier than the average for the period 1992 to 2016. In many parts of Ger- many, including the Lake Constance fruit-growing region, it even began before 15 April. In the case of cherry trees – whose average flowering date in Germany in 2017 was 6 April – it was as much as twelve days earlier than the long-term average (Fig. 1). The frost had a devastating impact because of the early start of the growing season in many parts of Europe. In the second half of April, it affected the sensitive blossoms, the initial fruiting stages and the first frost-susceptible shoots on vines.
Source – https://www.munichre.com/