In 2009, average temperatures above the norm, and in particular the extremely warm months of April, May and August, significantly influenced the development of vegetation in Switzerland. In contrast, the drought that prevailed temporarily did not influence this development. The growing season began in normal or time or slightly delayed with hazel flowering in March and coltsfoot late March – early April. Few weeks later, at the time of the last spring phenological phases, vegetation was early, in particular the daisy flowering. A warm April and unusually high temperatures in May are responsible for this turnaround. The early arrival of phenological summer was truly exceptional, with some new record dates. Thus, in summer 2009, due to the heat in May and August, an advance of vegetation development from two to three weeks compared to the standard was temporarily observed. Grape harvesting and Autumn crocus flowering took place at a very early date. In contrast, the fall of 2009 showed a clear trend to the late occurrence of autumnal phenological phases that are leaf colouring and leaf fall.