Summary:

An assessment of the variability of four climatic indicators of plant irrigation needs (air temperature, precipitation, frequency of atmospheric droughts, rainfall shortages) in the 1st zone of irrigation application in Poland was carried out. The analysis concerned four localities (Szczecin, Poznań, Kalisz, Toruń) during the reference multiyear period 1991-2020, in the entire period of active plant growth (V-VIII) as well as the parts of it. Results of the analysis have shown a fairly clear increase in irrigation needs in terms of the climatic criterion. It results primarily from a significant increase in air temperature, resulting in an increase in the water needs of plants. For the period 1991-2020 tendency to deepening rainfall shortages in the Szczecin Lowland and in Wielkopolska was demonstrated. The large numbers of atmospheric droughts with higher level of intensity were identified in the second part of the analysed period in the years 2015- 2020.