Long-term variability of bioclimatic conditions and tourism potential for Warsaw agglomeration (Poland).

The research area includes one of the largest in terms of population and also the most attractive tourist area in Poland-Warsaw agglomeration. The aim of the study is to assess the temporal and spatial difference of the heat stress on the human body in this area based on long-term data (1980-2016). On the basis of the Universal Thermal Climate Index (UTCI) and designated Climate-Tourism-Information-Scheme (CTIS) diagrams, a comprehensive and detailed bioclimate assessment was made for three different areas. The highest values of the UTCI as well as the frequency of thermal sensations related to heat stress occurred at the Bielany station representing the city area, and the lowest at stations representing suburban area-Legionowo and outskirts-Okęcie. A negative linear trend of the number of days was observed for thermal stress related to cold stress and the category of 'no thermal stress' while a positive linear trend was obtained for thermal stress related to heat stress. Based on the obtained results, it can be concluded that in summer months (in June over 60%) the conditions are favourable for the residents causing the lack or slight intensification of the body's adaptation processes and they are beneficial for practicing various forms of recreation and tourism. However, on the other hand, the rise in the number of days with the 'strong and very strong heat stress' especially at the station representing the city area is a disturbing factor and negatively affecting both the health and well-being of agglomeration residents in the future.