The paper presents the basic characteristics of the thermal conditions at the Ecological Station in Jeziory (Wielkopolski National Park) in 2006-2015. The aim of the study is to analyse the variability of day-to-day air temperature and to determine the nature of the stimuli of the thermal conditions. The average annual temperature in Jeziory in 2006-2015 was 9.1°C. In the course of annual air temperature, July was the warmest month with an average temperature of 19.7°C. The average maximum occurred often in August as well. The coldest month was January with an average temperature of –1.1°C. The average minimum occurred also in February and December. The greatest seasonal fluctuations in air temperature occurred in the winter. In the other seasons, the course of average temperature is more even. At the Ecological Station Jeziory, there are small interdiurnal changes of air temperature. Declines tended to be much more prominent than increases. The mean change for the entire period is close to zero (0.4°C). In most cases, these changes did not exceed ± 1.5 deg but in extreme cases they reached several degrees. The biggest interdiurnal changes occur in May and January. The smallest range of the changes occurred in July and March. The biothermal conditions in the surroundings of the station in Jeziory are conducive to the development of tourism and recreation. The analysed decade was dominated by inert (68%). The sharp thermal stimuli appeared rarely (2%). Significant and sharp stimuli occur usually in the winter i.e. in December and January and then in the spring: in April and May.

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