Abnormal meteorological events occur frequently under global climate change. As another unusual meteorological event, a warm-dry climate occurred in North China in spring 2016 after the extreme cold-wet weather in spring 2010. Phenological observations of the flowering phenology of Viburnum from 2009 to 2016 showed that flowering onset was advanced in the warm-dry spring in 2016, but flowering duration was never shortened over the observation years; and the variance in threshold on flowering onset, active accumulated temperature and flowering duration of species with narrow altitude spanning, for V. macrocephalum and V. opulus, for example, were very wide, whereas species with large altitude spanning, such as V. prunifolium, V. lantana and V. carlesii, presented limited plasticity on flowering onset, active accumulated temperature and flowering duration; moreover, the relative flowering onset among these 3 species did not change, whatever meteorologically occurred in spring over several years. As well, the allocation of assimilation on shoots increased by significantly increased shoot diameter and simultaneously increased leaf growth rate as compared with the normal year. However, leaves became much thinner than the normal year. The assimilation was allocated more to those leaves far from fruits experiencing a warm-dry event. Study of the flowering phenology responsive to extreme meteorological events at a given hierarchy can reveal an environmental plasticity of flowering during extreme climate change and provide basic information for classical phenological research.