This study analyses the responses of the different components of flora from a high-mountain area with a sub-desert climate to changeable meteorological conditions that may affect their normal development. Local airborne pollen levels are used as bio-indicators of the vegetation behavior. In order to determine the fluctuations in this status, a set of 6-year pollen data obtained using aerobiological methods was used. The results show that the tree species (Cupressus sp., Olea europaea; Quercus sp. and Platanus hyspanica) react differently to situations of water stress and changeable temperatures than herbaceous species (Urticaceae, Chenopodiaceae, Poaceae species and Artemisia sp.). The flowering of tree species seems to be affected more by conditions in the months prior to flowering, in particular for species flowering in winter-early spring. As important as the amount of rainfall is the distribution of rainfall throughout the year, since this ensures permanent water availability. Herbaceous species present the most immediate response to weather conditions and if rainfall occurs during their principal pollination period, this period lasts longer. Sometimes, under favorable conditions, non-seasonal flowering may occur.