The paper analyses the temporal and spatial variability of the Universal Thermal Climate Index (UTCI) in Poland in summer. Summer is the season with the highest intensity of tourism traffic that is why it is important to determine biometeorological conditions, especially in popular tourist destinations such as coastal, mountain and urban areas, in the times of climate changes. The analysis was based on data from 18 stations of IMGW-PIB (Institute of Meteorology and Water Management—National Research Institute), distributed evenly in the territory of the country, and representing all eight bioclimatic regions. The data include air temperature, relative humidity, wind velocity and cloudiness at 12 UTC from summer months: June, July and August from the years 2001–2018. Thermoneutral zone was the most frequently occurring UTCI class in Poland. It was recorded during 56–75% of summer days (with the exception of mountain stations, where it occurred on 30–35% of days). Moderate heat stress is the second most frequently occurring category with a frequency from 18 to 29% with the exception of mountain and coastal areas. Extreme and very strong cold stress occurred particularly in high mountain stations, and was sporadically observed at the coast of the Baltic Sea; however, the occurrence of such conditions decreases, which if favourable for beach tourism. No cases of extreme heat stress were recorded in any of the stations. The most unfavourable bioclimatic conditions were characteristic of the Upland Region (IV), represented by Kraków and Sandomierz, where very strong heat stress occurred with a 10% frequency. This is a limitation for urban tourism in those regions. The highest UTCI values were recorded in Kraków on 17 July 2007 and 29 July 2005. The highest number of cases with strong and very strong heat stress was recorded in 2015 as a consequence of the heat wave observed in Poland in the first half of August. In the majority of the analysed stations, in the second half of the analysed period (2010–2018), an increase in the number of days with strong and very strong heat stress was observed in comparison with the first half of period (2001–2009). The highest frequency of such days was observed in July. Based on the data, there are 4 potential periods of occurrence of such days, with two most intense being 26. July–13 August and 14–22 July.

The IPCC ( 2014 ) categorises heatwaves as extreme weather events. In the scientific literature, particularly long and severe heatwaves are described as ‘mega‐heatwaves’ (Barriopedro et al., 2011 ). The heatwave that occurred in Poland during the first half of August 2015 belongs to this category. The objective of this study was to analyse the thermal and biometeorological conditions (in terms of the UTCI index) for the period 3–16 August 2015 in selected Polish cities. Hourly data were available for 36 meteorological stations, which are evenly distributed across the country and represent all bioclimatic regions, according to K. Błażejczyk (Błażejczyk and Kunert, 2011 ). The data were obtained from SYNOP messages (see www.ogimet.com) and the IMGW database. The shortest‐duration heatwave observed in this study occurred at the stations within the coastal region (I). In cities located on the coast (among others, Koszalin and Łeba), conditions under which humans would experience heat stress were observed less frequently than elsewhere. No thermal stress conditions were recorded for the stations in the mountains (Kasprowy Wierch and Śnieżka). The longest heatwave, lasting 13 consecutive days, was observed at the stations at Łódź, Katowice and Opole, which are located in central Poland. The most severe biometeorological conditions were reported for this region. At Opole, there were 98 recorded cases (each case corresponds to an hourly measurement) of air temperature values in excess of 30°C, and 104 cases of UTCI values higher than 32°C. The heatwave peaked on 7/8 August; ‘strong heat stress’ and ‘very strong heat stress’ conditions were reported at 11 of the 36 stations for more than 10h. The highest values for maximum temperature (37.9°C) and UTCI (42.1°C) were recorded in Wrocław.

This study evaluates the relationship between atmospheric circulation conditions and the frequency of heat/cold stress in Lublin in the years 1951-2010 according to the Universal Thermal Climate Index (UTCI). The paper outlines the frequency and conditional probability of heat/cold stress during particular circulation types and analyses the circulation patterns that induce these incidences. Increased wind velocity had a significant effect on creating unfavourable bioclimatic conditions in winter. Meanwhile, in summer, heat stress was observed almost exclusively when a high pressure system from eastern Europe induced a slow inflow of very warm air masses from the east or south.

The study analyses spatial and temporal variability of the UTCI index during winter seasons in Poland in the 21st century. The most frequent UTCI thermal stress category was moderate cold stress with a frequency varying from 45.8% in Łeba (Coastal region) to 66.1% in Zielona Góra (Central region). In mountain areas, this class was less frequent (7.312.3%). The second most frequent class was strong cold stress with values from 11.1% in Zakopane (Carpathian region) to 43.4% in Suwałki (North-East region). In mountain areas, very strong cold stress and extreme cold stress occurred frequently (25.0-35.5% and 17.7-52.0%, respectively). Few cases of extreme cold stress were observed on other Polish stations. Thermoneutral zone was not recorded in the mountain area, although on other Polish stations its frequency ranged from 0.1% in Chojnice, Suwałki and Białystok located in northern part of Poland to 4.3% in Zakopane (Carpathian region).

This paper presents the analysis of medical rescue team interventions related to cases of hypothermia over the period 2008–2012 in a selected area of the Lublin Region, in southeast Poland. We compared the interventions to weather conditions, based on the bioclimatic Universal Thermal Climate Index (UTCI). This paper focuses on cases of hypothermia on days with at least slight cold stress, when the UTCI value is < 9°C. The results show that the most frequent interventions in cases of hypothermia are during relatively low heat load involving cold stress, corresponding with air temperatures (at low wind velocities) oscillating around zero (approximately ±5degC). Although we can prevent hypothermia and cold‐related diseases, even in the twenty‐first century there are people suffering due to cold. This paper contains advice for policymakers assisting the prevention of hypothermia in the most vulnerable groups of society.