Sunshine duration (SD) is an essential meteorological variable. It represents the sum of time for which direct solar radiation with an intensity above 120 W center dot m-2 reaches the Earth's surface. In the contemporary observational routine, automatic electronic devices are in use. The pyranometric method based on global solar radiation measurements (Kglob) is also proposed by the WMO to assess SD. The aim of the paper is to study the accuracy of the Slob-Monna method (SD-WMO), recommended by the WMO to calculate sunshine duration. Alternatively, the author's method, which is based on the & Aring;ngstr & ouml;m clearness index (SD-ACI), was used to approximate SD. For this purpose, a two-year series of SD and Kglob observations at four locations in Poland (well representing the Central European transitional climate zone) was analyzed. The result shows that, for SD-WMO, sunshine duration values are on average 16% higher than observed ones. For the SD-ACI method, they are only 5% higher. When verifying the accuracy of SD-WMO and SD-ACI approximations, we have found that, both for daily and monthly periods, the calculated SD sums are closer to the observed ones in the case of SD-ACI than for the SD-WMO method. The correlation coefficients are, respectively, 0.98 and 0.82 for daily sums and 0.99 and 0.88 for monthly sums.

Obszary górskie, w tym Tatry, są ważnym elementem krajobrazu. Ich wyróżniającą się cechą jest strefowość wysokościowa wszystkich elementów środowiska: rzeźby terenu, pokrywy glebowej, szaty roślinnej i klimatu. Celem artykułu przedstawienie dwóch aspektów bioklimatu obszaru Tatr: i) bioklimatu roślin, a mianowicie interakcji zachodzących pomiędzy roślinnością acidofilną a lokalnymi cechami rzeźby i mikroklimatu w piętrze subalpejskim i alpejskim Doliny Suchej Wody, oraz ii) bioklimatu człowieka, a mianowicie pokazanie, w jaki sposób lokalne i regionalne czynniki geograficzne wpływają na stres termiczny w Tatrach. Badania dotyczą różnych skal przestrzennych (mikro- i regionalnych) i czasowych (krótkoterminowych i wieloletnich). Terenowe badania klimatyczno-roślinne prowadzono w górnej części Doliny Suchej Wody na zboczach Beskidu i Uhrocia Kasprowego, porośniętych naturalną roślinnością acidofilną, typową dla strefy alpejskiej i antropogeniczną (po wypasie) w strefie subalpejskiej. Interakcje pomiędzy cechami mikroklimatu, będące efektem specyficznych cech bilansu radiacyjnego, a istniejącą pokrywą roślinną kształtowały gradienty temperatury powietrza przy powierzchni gruntu, które były istotnie modyfikowane przez ekspozycję zboczy i lokalne czynniki siedliskowe związane z rzeźbą terenu (obecność bloków skalnych, zagłębień i płatów śniegu). Gradientom temperatury towarzyszyło stopniowe przechodzenie roślinności strefowej, typowej dla pasów subalpejskiego i alpejskiego. Badania bioklimatu człowieka uwzględniają regionalną zmienność stresu termicznego, określonego za pomocą wskaźnika UTCI, w północnej i południowej części Tatr. Wysokościowa strefowość obciążeń termicznych jest modyfikowana przez położenie w stosunku do głównego grzbietu. Gradienty UTCI są wyższe niż gradienty temperatury, szczególnie w obszarze północnym. Na północnych skłonach Tatr są one znacząco większe niż na skłonach południowych.

Thermal stress indices play a vital role in evaluating human health risks related to heat and cold. Mean Radiant Temperature (MRT), derivable from numerical weather prediction (NWP) models, is a critical input for many such indices. This research generates high-resolution (5.5 km × 5.5 km) MRT estimates across Europe using the CERRA NWP system. We evaluate different computational approaches, benchmark the high-resolution MRT against the established ERA5-HEAT dataset, and validate results using BSRN ground observations. The study focuses on diverse European environments. Our high-resolution MRT product demonstrates comparable performance to ERA5-HEAT over flat terrain but offers substantial accuracy gains over complex terrain, including mountainous and coastal regions. These findings highlight the value of enhanced spatial resolution for accurate MRT estimation, crucial for robust thermal stress assessment and contributing to improved environmental health and safety strategies.

Recent decades have brought increasing effects of climate change and variation. Climate changes, indicated by various bioclimatic indices, influence the functioning of living organisms, including humans. Previous studies have documented multiyear fluctuations in such indices. In this study, we employ the Universal Thermal Climate Index (UTCI), a recently developed bioclimatic indicator designed to condense complex thermodynamic and meteorological conditions into a single value representing specific categories of thermal stress. The average annual UTCI values for the period 1826-2021 in Krakow, Poland, increased at a rate of 0.27 degrees C per decade, with the most pronounced rise observed during the winter season, as documented in prior studies. However, when considering the more recent period of 1951-2023, the trend intensifies significantly, reaching 0.61 degrees C per decade, indicating a clear acceleration in bioclimatic warming. In the present study, we apply an automatic recurrence plot (RP) analysis method to investigate these changes in human bioclimate. We introduce a novel approach by automating RP interpretation with a genetic algorithm and statistical deterministic analysis, thereby providing readers with ready-to-use algorithms. The research focuses on a univariate time series of UTCI recorded from 1951 to 2023 in three locations in Poland-a key region of Central Europe where air masses from different parts of the continent interact. The main conclusion from the analyzed data is the identification of a date range (1980-1990), making a phase-transition-type passage between two periods that differ in statistical behaviors of UTCI. This bioclimatic change led to an increase in the frequency of very strong heat stress events and a decrease in the occurrence of very strong cold stress days. The RP analysis demonstrates that the data from 1990 differ most from data from the preceding period 1952-1965. This provides details of the findings reported in previous research regarding climate change in Poland. This discovery of a distinct transitional period marking a shift in the climatic regime in Poland, based on RP analysis, enriches existing knowledge on regional climate change with new empirical evidence.

Since 1989, Warsaw has been experiencing major changes in its urban space. Both the intensity of development in the city and urban sprawl have been growing. Consequently, the intensity of the urban heat island (UHI) has increased. This paper presents the current state of the UHI in Warsaw based on data from in-situ air temperature measurements conducted at 29 sites. This study intended (1) to analyse and evaluate the development and extension of the UHI in Warsaw between 2001 and 2018 and provide a UHI projection for 2050 and (2) to indicate UHI intensity in land functionality types, making it possible to predict the development of the UHI accompanying the development of the city. The annual average UHI in the centre of Warsaw was 3.6 degrees C, varying from -0.2 degrees C in the forests, which were cooler than the reference site, through 1.2 degrees C in other green areas, up to 2.3 degrees C within multi-family housing developments with higher greenery participation. The mean maximum intensity of the UHI was 8.4 degrees C. Taking into account the RCP4.5 and RCP8.5 scenarios and planned urban development, maps of future spatial UHI distribution were created and changes (%) in the area covered by different UHI intensities were calculated.

Study aim: This study aimed (i) to describe psychomotor parameters for different temperature and humidity conditions, and (ii) to verify whether conditions at the borderline between some and great thermal discomfort on the humidex scale affect psycho-motor parameters in soccer players.Material and methods: Twenty-four male soccer players aged 21.02 +/- 3.22 years from a Polish 4th league club performed a graded treadmill running exercise test. Directly before the test and during the break after each load, blood was collected to determine lactate concentration ([LA]) and serotonin concentration (SER). The heart rate (HR), pulmonary ventilation (Ve) and oxygen up-take (VO2) were recorded and the psychomotor test was performed. Measurements were carried out: (1) at rest, (2) at the lactate threshold (T[LA]), (3) at the threshold of psychomotor fatigue (TPF), and (4) at maximum intensity. Percentage differences between maximum intensity (100%) and the values of the tested parameters recorded at the T[LA] and TPF were also calculated. The tests were conducted in a climatic chamber at an ambient temperature of 28.5 degrees C, with a relative air humidity of 58.7%.Results: It was confirmed that the TPF, which reflects the highest efficiency of the central nervous system, occurs at a higher running speed than the T[LA]. For practical application, it was found that at the HSL, the TPF occurs at: 84% of maximum running speed, 52% of maximum [LA] concentration, 93% SERmax, 91% HRmax, 73% VEmax, 84% VO2max.Conclusion: Understanding the psychomotor and physiological responses of soccer players at the borderline between some and great thermal discomfort (on the humidex scale) can support coaches in optimizing training sessions to prepare players for playing in more challenging climatic conditions.

The majority of research dealing with the impacts of the Himalayan climate on human physiology focuses on low air temperature, high wind speed, and low air pressure and oxygen content, potentially leading to hypothermia and hypoxia. Only a few studies describe the influence of the weather conditions in the Himalayas on the body’s ability to maintain thermal balance. The aim of the present research is to trace the heat exchange between humans and their surroundings during a typical, 6-day summit attempt of Mount Everest in the spring and winter seasons. Additionally, an emergency night outdoors without tent protection is considered. Daily variation of the heat balance components were calculated by the MENEX_HA model using meteorological data collected at automatic weather stations installed during a National Geographic expedition in 2019–2020. The data represent the hourly values of the measured meteorological parameters. The research shows that in spite of extreme environmental conditions in the sub-summit zone of Mount Everest during the spring weather window, it is possible to keep heat equilibrium of the climbers’ body. This can be achieved by the use of appropriate clothing and by regulating activity level. In winter, extreme environmental conditions in the sub-summit zone make it impossible to maintain heat equilibrium and lead to hypothermia. The emergency night in the sub-peak zone leads to gradual cooling of the body which in winter can cause severe hypothermia of the climber’s body. At altitudes < 7000 m, climbers should consider using clothing that allows variation of insulation and active regulation of their fit around the body.

This study aims to measure the daily melatonin secretory rhythms of people living in high-, mid-, and low-latitude regions characterised by different day lengths and global solar-radiation conditions. In Poland, a high-latitude region, the amount of melatonin secretion is greater, with secretion occurring earlier (exemplifying phase advance). On the other hand, in Vietnam, a low-latitude region, the level is lower and occurs later (phase delay). Japan, a mid-latitude region, shows behaviour intermediate between these two. Melatonin secretory rhythm in Vietnam is closely related to Day length and Global Solar Radiation, though no such relationship is observed in Poland or Japan, making it necessary for other factors to be considered. The results of this study have important implications considering the impacts of light pollution and lighting-related conditions of modern life.

The set of meteorological data from the Jagiellonian University station in Kraków is one of the longest‐recorded in central Europe. Measurement records date back to 1826. Based on the average monthly values of air temperature, total cloudiness, water vapour pressure and wind speed at 1200 UTC, the UTCI values were calculated and the occurrence of cold stress (UTCI < −13°C) and heat stress (UTCI > 32°C) was estimated. The variability of the applied measures of thermal stress conditions was studied both annually and in individual seasons (MAM, JJA, SON, DJF). Statistically significant changes in the studied characteristics of the bioclimate were found. Average annual UTCI values increased at the rate of 0.27°C/10 years. In individual seasons, the trend of UTCI changes ranged from 0.10°C/10 years in summer to 0.43°C/10 years in winter. The number of days with cold stress decreased by 1.8 days/10 years and the number of days with heat stress significantly increased (0.5 days/10 years). Two subperiods with different trends of changes were determined. The first covers the years 1826–1940, and the second, 1941–2021. The former indicates a negative UTCI trend of −0.17°C/10 years, and the latter, an increasing trend of 1.09°C/10 years. The last eight decades have brought a decrease in cold days of 6.5/10 years and an increase in heat days of 2.6/10 years.

The study aimed at finding relationships between lactate threshold and psychomotor fatigue threshold during incremental exercise in thermo-neutral climate conditions and conditions for the 2022 FIFA World Cup in Qatar simulated in an environmental test chamber. The study included 24 soccer players aged 21.02 ± 3.22 years old. The following procedures were performed: The incremental exercise test to mark lactate concentration—LA (mmol·l−1); Psychomotor test to determine choice reaction time; Designation of the lactate threshold (TLA) and psychomotor fatigue threshold (TPF). Climate conditions: The procedure was performed twice in the climatic chamber: (1) in thermo-neutral conditions—TNC (ambient temperature 20.5 °C and relative air humidity 58.7%), (2) after 7 days—in Qatar conditions—QC (28.5 ± 1.92 °C) and (58.7 ± 8.64%). It was confirmed that the TPF, which reflects the highest efficiency of CNS functioning, occurs at a higher running speed than the TLA. The temperature of 28.5 °C with 58.7% humidity, which is the lower limit of heat stress, causes the psychomotor fatigue threshold to appear at a lower running speed than in thermoneutral conditions. The data recorded in this work may help to understand the specificity of physiological and psychomotor reactions to various climatic conditions.

Przedstawiony zbiór tekstów nie wyczerpuje oczywiście całości zagadnienia wpływu klimatu na funkcjonowanie wrażliwych ekosystemów i na funkcjonowanie społeczeństw. Wierzymy jednak, że dobitnie mówią one o konieczności zintensyfikowania działań społeczności międzynarodowej w kierunku zahamowania, a przynajmniej spowolnienia zmian klimatu. W przeciwnym razie grozi nam zniszczenie bioróżnorodności ekosystemów oraz kosztowne społecznie i ekonomicznie wysiłki zapewnienia przyszłym pokoleniom możliwości życia i rozwoju.

Artykuł identyfikuje fazy występowania zmian klimatu na obszarze Bliskiego Wschodu w dwóch perspektywach czasowych: 3000-0 BC oraz zmian współczesnych. W tym celu wykorzystano różne zbiory danych: 1) informacje zaczerpnięte z licznych badań i dokumentów archeologicznych i historycznych, 2) bazy indexu NAO i opadów atmosferycznych okresu zimowego (DJFM) za lata 1890-2020, 3) średnie miesięczne i roczne wartości temperatury powietrza (Tmean) dla 6 stacji w Iraku za okres 1941-2020. W perspektywie millenialnej zidentyfikowano 4 okresy znaczących faz chłodnych i suchych (2650-2500, 2200-1900, 1300-1200 i 1000-850 BC). Fazy te cechowały się dużą ostrością klimatu, co spowodowało znaczące zmiany społeczno-polityczne na obszarze Mezopotamii. Badania współczesnych zmian klimatu sugerują ujemne korelacje pomiędzy zimowym wskaźnikiem NAO i opadami, a w ostatnich 80 latach - dodatnie trendy temperatury powietrza wynoszące nawet 0,9°C/10 lat.

Climate change is a fact that worries the international community. The progressive increase in air temperature and the frequency and intensity of extreme weather events are felt by everyone.

This paper assesses changes in bioclimatic conditions in Poland using two indices: the Universal Thermal Climate Index (UTCI) and Physiological Subjective Temperature (PST). The indices were calculated using the BioKlima 2.6 software package on the basis of several meteorological parameters (temperature, humidity, cloudiness, wind speed), measured daily at 12:00 UTC, from the period 1951–2018 at 24 stations representing different biometeorological regions. First, the spatial distribution of UTCI and PST values and the frequency of different thermal stress and thermal sensation categories are presented, with the various thermal stress and sensation categories grouped into 3 for each index. Then, the absolute values and relative percentage trends (compared to 1951) are calculated for ten-year periods and days with specific characteristics. The analysis shows a significant increase in the minimum and mean values of the applied indices during the period under investigation over all areas of Poland, including the mountains, especially in the north-east (where UTCI minimum values rose up to 1.8 °C per decade) and Tarnów in the south-east (up to 2.2 °C per decade). The rise of UTCI summer maximum values was significant only in the north-east and north-west of Poland (0.3–0.5 °C per decade) and in the mountain foothills (0.3–0.4 °C per decade). The changes in PST maximum values were insignificant. On average, in every decade, the number of cold days reduced by 2.7 in the case of PST and 3.2 on the UTCI. However, in the north-east, the reduction was much greater, at 7 days per 10 years (UTCI) and 6 days when considering PST. Regionally, the greatest increase in the mean and minimum values of the indices used and the decrease in the frequency of cold days were observed in north-eastern, eastern and western Poland, i.e. the regions most exposed to frequent changes in air circulation, which is hypothesised to play the main role in shaping bioclimatic conditions in Poland.

Artificial light has been present in human life for decades but our knowledge of its effects is still insufficient. Lighting lets us be active longer, gives us a sense of security and provides aesthetic experiences. Despite all of these advantages, in urban areas artificial light also has a negative effects on the environment and human life. Although light pollution is one of the most common forms of anthropogenic environmental change, this phenomenon remains insufficiently investigated. The present work thus focuses on night sky brightness and artificial factors impacting the level of the phenomenon using Warsaw (Poland) and Fukuoka (Japan) as an example. The basis of the study is the new World Atlas of Artificial Night Sky Brightness. Moreover, we used image data from the Visible Infrared Imaging Radiometer Suite Day/Night Band and data from field research to analyse the primary artificial light characteristics in the two cities: illumination, colour temperature, peak wavelength, dominant wavelength, stimulation of photoreceptors, design of lighting fixtures and radiance. The results indicate that Warsaw (area: 517.2 km2; population: 1 777 972) is characterized by higher light pollution than Fukuoka (area: 343.5 km2; population: 1 554 229). Skyglow is primarily influenced by the number of light sources; however, local differentiation of the phenomenon depends on the spectral characteristics and design of lighting fixtures. Moreover, environmental features may affect light pollution through scattering, reflection and absorption. Outdoor lighting in Warsaw was characterized by a higher value of light illumination and greater stimulation of photoreceptors sensitive to long and medium waves. However, the lighting infrastructure in Fukuoka was also unsuitable, as it was characterised by high values of colour temperature and stimulation of photoreceptors sensitive to short waves and ganglion cells, which may be detrimental to the human body.

UTCI, although it was developed with the participation of scientists from 22 countries, it has shortcomings and people using it face various obstacles. The difficulties include wide range of issues: from different availability of meteorological data in individual countries, through the kind of air temperature which should be properly used in calculations, or the need of recalculation of wind speed. However the biggest subject concern algorithms for mean radiant temperature (Mrt) calculations, different models and programs which simplify calculations of this complex index though introduce different approximations and, as a result, many false results. The paper presents also wide range of UTCI applications in urban bioclimate studies and bioclimatic mapping, climate-human health researches and biometeorological forecasts which were the primary purpose of the index creation, but also applications in tourism and recreation or even in bioclimate change analysis.

W opracowaniu przedstawiono warunki cyrkulacyjne i wybrane charakterystyki opadów atmosferycznych oraz ich natężenie w Tatrach i Czarnohorze. Zbadano zależności natężenia opadów od cyrkulacji atmosferycznej. Wykonano porównanie opadów w analizowanych masywach w ciągu ostatnich lat, także w kontekście zmian cyrkulacji atmosferycznej. Oceniono, czy i na ile zmieniła się w badanym okresie intensywność opadów. Zastosowano klasyfikację typów cyrkulacji atmosferycznej Niedźwiedzia (2017). Obliczono, roczne wartości wskaźników cyrkulacji P (przepływ zachód-wschód), S (przepływ południe-północ) i C (sytuacja cyklonalna/antycyklonalna). W opracowaniu wykorzystano dobowe sumy opadów ze stacji Pożyżewska (PO, 1451 m n.p.m., φ 48˚09’N i λ 24˚32’E) położonej na północno-wschodnim skłonie Czarnohory i stacji Hala Gąsienicowa (HG, 1520 m n.p.m., φ 49°14’N i λ 20°00’E) leżącej na północnym skłonie Tatr, za okres 1961‑2015. Największe zmiany zaobserwowano w przypadku wskaźnika napływu strefowego P i wskaźnika cykloniczności C. Ogólnie, trend rocznych sum opadów jest dodatni, ale nie jest istotny statystycznie. Trend zmian liczby dni z opadem jest ujemny zarówno w Czarnohorze, jak i w Tatrach (-7,3 dni/10 lat i -7,59 dni/10 lat, odpowiednio). Natomiast trend zmian liczby dni z opadem o większym natężeniu, np. >10mm jest dodatni w Czarnohorze (+1,23 dni/10 lat) i ujemny w Tatrach (-0,6 dni/10 lat).

While significant increases in air temperature are being observed in the context of climate change, precipitation characteristics, indicators and indices seem to be changing in a more regionally-variable manner. High-mountain areas prove particularly subject to fluctuations and changes of climate, given that mountains serve as barriers to masses of air flowing over them, with the result that atmospheric precipitation totals are high in the context of the so-called orographic rainfall. Overall, the Chornohora represents the highest range anywhere in Ukraine’s Carpathian Mts, as there are six peaks over 2000 m a.s.l. capable of serving as a barrier running NW-SE. Nevertheless, the main ridge of the High Tatras (of the Slovakia-Poland borderland) is even higher and runs W-E. Each massif is some 30 km in length, while the two ranges are separated by a distance of almost 350 km. Main drainage divides run along the highest ridges here, with the Tatras separating the drainage basins of the Vistula and Danube, while the Chornohora represent a divide between the Prut and Tysa basins. The aim here has been to present characteristics of atmospheric precipitation in Tatra and Chornohora Mts. as these are seen to relate to atmospheric circulation. To this end, the dependent relationship between intensity of precipitation and atmospheric circulation was examined exhaustively, with changes in the latter considered from the point of view of intensity of precipitation in the massifs under study, and with trends for precipitation over the study period also looked for.The Niedźwiedź (2017) classification of types of atmospheric circulation was applied, with annual values calculated for circulation indicators P (a W-E inflow), S (a S-N inflow) and C (a cyclonic/anticyclonic inflow). Overall, the study drew on 1961‑2015 daily precipitation data from the north-eastern slope of Chornohora Mts. (as represented by Ukraine’s Pozhyzhevska weather station, PO, 1451 m a.s.l.), as well as the north slope of the Tatra Mts. (as represented by Poland’s Hala Gasienicowa weather station, HG, 1520 m a.s.l.).An air inflow from western directions was found to have prevailed over 28% of the days in the average year (Fig. 1). The most frequent types involved here were: Ka (12%), Bc (10%), Wc (10%) and Wa (8%). During the summer months (JJA), it is the Ka and Bc types that are even more frequent (present on approx. 15% of summer days). Types Wc and Wa in turn occur more frequently in winter (DJF) – respectively 13% and 12% of the time. In autumn, these types reach a level of occurrence around 10%.At 1712 mm, the average annual rainfall total for Tatra Mts is higher than that for the Chornohora (on 1446 mm). While the seasonal distribution of rainfall in spring and autumn looks almost the same in the two massifs, winter brings more precipitation in the Chornohora, while summer is a wetter season in the Tatras (Fig. 2). Largest amounts of precipitation nevertheless fall in the warm half-year, in the circumstances of N+NEa advection, cyclonic situations and under arctic, polar-marine or polar-marine transformed air masses (Figs. 3 and 4).The largest changes over time are to be observed for the zonal inflow index (P) and the cyclonic index (C). The P index points to increased numbers of days with a western circulation, while the C index confirms the domination of anticyclonic circulation (Fig. 5). The trend for annual rainfall totals is an upward one overall in both regions, but in neither does this achieve statistical significance (Fig. 6). Equally, there is a downward trend line for numbers of days featuring precipitation (RRdays) in the cases of both the Chornohora and Tatra ranges (equal to -7.3 days/10 years and -7.59 days/10 years respectively) (Fig. 7). On the other hand, the trend for numbers of days with higher rainfall, e.g. with RRdays>10mm is upward for the Chornohora (at +1.23 days/10 years), but downward for the Tatra Mts (at -0.6 days/10 years) (Fig. 8).

The occurrence of long-lasting severe heat stress, such as in July-August 2003, July 2010, or in April-May 2018 has been one of the biggest meteorological threats in Europe in recent years. The paper focuses on the biometeorological and mortality effects of the hot June that was observed in Central Europe in 2019. The basis of the study was hourly and daily Universal Thermal Climate Index (UTCI) values at meteorological stations in Poland for June 2019. The average monthly air temperature and UTCI values from 1951 to 2018 were analysed as background. Grosswetterlagen calendar of atmospheric circulation was used to assess synoptic conditions of heat wave. Several heat strain measures were applied : net heat storage (S), modelled heart rate (HR), sultriness (HSI), and UTCI index. Actual total mortality (TM) and modelled strong heat-related mortality (SHRM) were taken as indicators of biometeorological consequences of the hot June in 2019. The results indicate that prolonged persistence of unusually warm weather in June 2019 was determined by the synoptic conditions occurring over the European region and causing advection of tropical air. They led to the emergence of heat waves causing 10% increase in TM and 5 times bigger SHRM then in preceding 10 years. Such increase in SHRM was an effect of overheating and overload of circulatory system of human organism.

The assessment of thermal stress stimuli in Poland was based on the Universal Thermal Climate Index (UTCI). Daily values of UTCI at 24 stations selected to represent the whole area of Poland at 12:00 UTC were calculated over the period 1951-2018. Various UTCI characteristics, i.e., spatial averages of daily, monthly and annual values, daily spatial contrasts (i.e., the difference between daily highest and lowest UTCI values) were defined in each of 8 bioclimatic regions of Poland. Ten-year trends for UTCI and spatial contrast values were counted and their statistical significance was analysed. A statistically significant increase in UTCI values was found in all the regions of Poland. However, contrasts in thermal stress both for Poland as a whole and in most of the regions decreased significantly, especially in the north-east of Poland, the country's coldest region. This indicates a reduction in the stimuli of thermal environment in Poland and in most of the individual regions.