The Length of the Beach Season at Lake Balaton—An Estimation Based on Operative Temperature

The length of the beach season at Lake Balaton (Hungary, Central Europe) in the period 2002–2024 is estimated using daily data of air temperature, water temperature and wind speed. Daily thermal load is approached by calculating operative temperature using operative temperature-air temperature relationships on monthly scale. We introduced the concepts of beach day and bath day in order to estimate when the environmental conditions were suitable for lakeside activities. Data are taken from meteorological station Siófok. The main results are as follows. In the summer months, the median number of beach days and bath days is 72 and 68, respectively. The unbiased standard deviation of beach days and bath days is 4.62 and 6.4 days, respectively. As regards bath days, the best year was 2023, then the number of bath days was 105. The smallest number of bath days was 57; this occurred in the year 2010. As regards beach days, the best year was 2018 with 114 days, the worst year was 2021 with 72 days.