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The paper focuses on exceptionally hot summers (EHS) as a manifestation of contemporary climate warming. The study identifies EHS occurrences in Central and Eastern Europe and describes the characteristic features of the region's thermal conditions. Average air temperatures in June, July and August were considered, as well as the number of days with maximum temperatures exceeding 25, 30 and 35°C, and with a minimum temperature greater than >20°C, as recorded at 59 weather stations in 1951-2010. Extremely hot summers are defined as having an average temperature equal to or greater than the long-term average plus 2 SD. A calendar of EHSs was compiled and their spatial extent identified. The region experienced 12 EHSs, which occurred in a given year at 5 % or more stations (1972, 1981, 1988, 1992, 1997, 1998, 1999, 2002, 2003, 2006, 2007 and 2010). The EHS frequency of occurrence was found to be clearly on an increase. Indeed, only one EHS occurred during the first 30 years, but these occurred five times during the last 10 years of the study period. Their geographical extent varied both in terms of location and size. EHSs were observed at 57 out of the total of 59 weather stations in the study (the exceptions were Pecora and Cluj). The average air temperature of EHSs tended to exceed the relevant long-term average by 2-4°C. The summer of 2010 was among the hottest (temperature anomaly 5.5-6°C) and spatially largest.

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Contemporary climate warming is a key problem faced not only by scientists, but also all by humanity because, as is shown by the experience of recent years, it has multiple environmental, economic and biometeorological implications. In this paper, the authors identify the magnitude of annual and seasonal temperature changes in Europe and its immediate surroundings on the basis of data from 210 weather stations from 1951 to 2020. An analysis of temperatures in the 70-year period shows that air temperature has continued to grow linearly in Europe since 1985. The rate of temperature rise in three seasons of the year, namely winter, spring and summer, does not differ greatly. The highest growth over the 1985–2020 timespan was recorded in spring and the lowest in autumn—0.061 °C/year and 0.045 °C/year, respectively. In winter, the rise in temperature should be considered the least steady, as opposed to the summer when it displays the greatest stability. Overall, the warming intensifies towards the north-east of the continent. Such a strong gradient of change is especially perceivable in winter and spring, and is also marked in autumn. The opposite is true in summer, when it increases towards the south and south-west.

The paper discusses the impact of atmospheric circulation on the occurrence of various types of precipitation. A 146-year-long precipitation record from Kraków spanning the period 1863-2008 was used alongside a calendar prepared by Niedźwiedź (1981Niedźwiedź ( , 2009) describing circulation types covering the period 1873-2008 and air masses and atmospheric fronts covering the period 1951-2008 in southern Poland. The influence of atmospheric circulation on precipitation was measured using the frequency, conditional probability and average daily totals of precipitation. Circulation types, air masses and atmospheric fronts exerted influences on precipitation as a result of the seasonal variations of the thermal and moisture properties of air masses. The impact is best expressed by circulation types as these combine the aspect of cyclonicity/anticyclonicity with that of the direction of air advection, the two elements which determine the physical properties of the air. On average, liquid precipitation prevailed in all circulation types, except the Ea type in which snowfall dominated over liquid precipitation. Depending on the season, one of the three types of circulation, Wa, Wc and Bc, were shown to coincide with the greatest amount of liquid and thunderstorm precipitation. There was no single dominant circulation type for mixed precipitation or snowfall. In summer, the circulation types Nc, NEc, Cc and Bc were the most favourable to liquid and thunderstorm precipitation in terms of both probability and totals. In winter, snowfall was the most favoured by the Ec type. Frontal precipitation was twice as likely to occur as air mass precipitation, with the exception of snowfall which was predominantly an air mass type of precipitation in terms of probability, but its greatest totals were recorded on atmospheric fronts.