The chapter presents changes in air temperature and precipitation in the Upper Vistula Basin. Data from 18 meteorological stations covering the 1951–2015 period was used to investigate variability and trends in air temperature, precipitation and linkages between them. Air temperature in the Upper Vistula Basin was significantly rising during the research period. Distinct warming on annual scale started in the first half of the eighties. Spring and summer air temperatures have been significantly increasing; winter air temperature trends were much weaker while no significant changes were found in autumn. Upward trends in air temperature within the Upper Vistula Basin were also reflected in the frequency of thermally characteristic days which was significantly changing during the research period. Strong downward trends were found in the frequency of winter days (Tavg ≤ 0 °C) while trends in warm characteristic days were positive. Most observed changes in precipitation were not statistically significant at the level of 0.05. This indicates that significant increase in air temperature is not currently accompanied by significant increase in precipitation thus changes in precipitation are not directly related to changes in air temperature and they possibly vary in time. Relations between precipitation and air temperature are not straightforward. The results indicate that strong increase in air temperature is rather accompanied by decrease in precipitation frequency and amount. However, this applies only to overall precipitation totals and not to extreme events which are random and can occur unexpectedly. Flood precipitation can also occur during drier periods, as in the last decade of the research period. It however must be mentioned that for nearly all stations mean precipitation totals from the warmer period of 1991–2013 (1991–2011) were higher than in previous period 1961–1990. Moreover the study revealed that increasing, statistically significant, trend (from 0.15 to 0.24 °C/decade) in mean annual air temperature likely impacted changes in heavy precipitation. The links between air temperature ranges (0–10, 10–20 °C and above 20 °C) and precipitation ranges (0–10 mm, 10–20 mm, etc. to above 50 mm) for two periods examined at nine stations in the Upper Vistula Basin revealed that when air temperature exceeded 20 °C more intense precipitation was observed in the second warmer period 1991–2013.