Meteorologischer und phänologischer Jahresrückblick 2009 | Meteorological and phenological annual review for 2009

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 time or slightly delayed with hazel flowering in March. Few weeks later, at the time of the last spring phenological phases, vegetation was early, in particular the beech leaf unfolding. 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 of two to three weeks compared to the standard was temporarily observed. Unlike most previous years, the fall of 2009 showed a clear trend to the late occurrence of autumnal phenological phases that are leaf colouring and leaf fall.