Climate change is a very serious threat, and its consequences affect many different aspects of our lives. In Slovakia, we will also have to get used to the faster onset of warm and dry weather in the spring. The year, from a temperature point of view, ended as the 2nd warmest since 1931. Statistically very significant (annual) deviations occurred in the entire territory of Slovakia, so we characterize it in terms of temperature as strongly to extremely above normal. We monitored the influence of climatic conditions on the dendrometric changes of 9-year-old royal walnut (Juglans Regia L.) in Nove Zamky (Slovakia). The research took place in the spring and summer months of 2023 (April 1 - July 31, 2023) and trees were compared a) non-irrigated (only with natural precipitation) and b) irrigated (irrigation dose of 30 mm after the soil water potential drops below 80 kPa). Dendrometric changes were recorded with a DD-S device (Ecomatik) in hourly intervals. Parameters such as temperature, precipitation and soil moisture in 20 cm were also recorded. From the results, in the observed period the growth of branches in the irrigated variant is 3.66 mm, while in the non-irrigated variant it is only 1.24 mm. Although there is a greater increase in the diameter of the branches in the irrigated variant, in the summer (July), when the average daily temperature is also higher, the daily fluctuation of the diameters is higher than in the non-irrigated variant, which is caused by higher evapotranspiration. Based on these results, it is possible to set the optimal use of irrigation in the future based on the needs of plants and not only according to the soil water potential.