Global climate change has unforeseeable ramifications for the ecosystem of our planet Earth. In Europe, more than half of the vascular plant flora may become endangered by the year 2080 as a result of climatic changes. According to the Copernicus Program’s study of European municipalities, Budapest is one of the most affected cities by global warming. Urban climate conditions are considered similar to the changing global climate conditions. To find out how excess heat in urban environments affects the phenological flowering patterns of species we planted specimens representing 6 different life-forms of the Raunkiær system (phanerophytes, chamaephytes, hemicryptophytes, geophytes, hemitherophytes, therophytes). The species of the ex situ experiment were planted in two different mesoclimatic locations, in the ELTE Botanical Garden, Budapest and in the Hungarian University of Agriculture and Life Sciences Gödöllő Botanical Garden. Each life-form was represented by at least 5 species and each species by 5-5 specimens in both locations. By recording phenological data we followed Primack’s method. All the species in the experiment showed an average of 7.62 days earlier flowering onset in Budapest. The maximum of the flowering showed 12.94 days of difference, while the end of flowering showed 2.9 days of difference, with the earlier being Budapest. There is a strong significant difference (P ˂ 0.001) in the onset of the flowering of Globularia cordifolia between the locations, regarding the peaks of flowering there is a strong significance (P ˂ 0.001) for Inula ensifolia, regarding the end of flowering there is a strong significance (P ˂ 0.001) for Polygonatum multiflorum. The average duration of the flowering of all species was 4.72 days longer in Budapest compared to Gödöllő. To clarify other driving forces and the role of abiotic parameters in the flowering phenology patterns, further study is required.