It is commonly believed that weather conditions affect human mood and many believe that they are happier when days have longer sunny intervals, rather than days which are shorter, darker, and rainy. The contemporary man, besides wanting to know what the weather is going to be like in a day, two or more days, wants to know if and how the weather is going to affect him. The answer to that question is given by bio-prognosis, which describes the conditions that are created under the influence of weather that have an influence on healthy people, mood, and other. The aim of this research is to determine whether the influence of seasons and adverse weather conditions affects the number of hospitalizations related to mood disorders. The study was based on retrospectively collected data of 261 respondents hospitalized at the Department of Mental Health OB "Josip Benčević" in Slavonski Brod during adverse weather conditions in the time period from 01.01.2015 to 31.12.2016. The research used the data of the Croatian Hydrometeorological Institute on the daily bio-meteorological conditions for the city of Slavonski Brod for the observed time period. According to the results of the research, 88 of the total number of respondents were men, while the incidence of women (173) with symptoms of mood disorders is larger. There was no statistically significant difference between the adverse bio-meteorological conditions and their impact on the number of hospitalizations in relation to gender, neither in relation to the age of the respondents, but also in the correlation between the seasonal changes and the number of hospitalizations related to mood disorders. The fact is that certain physiological and psychopathological processes have changed significantly during certain periods of the year or seasons, suggests direct exposure to climate variables. However, this can also be an expression of an autonomous biorhythm and the question remains of whether climatic conditions and climate variables have an impact on the mental state of humans. Scientists explains today's meteoropathy through the modern way of life that is far from nature. They believe that people mostly live in closed, air-conditioned spaces, and this way of life often reduces the ability of natural adaptation of our bodies to different environmental conditions. The human body is accustomed to closed spaces, which are often heated in the winter and cooled down in the summer, so self-regulation mechanisms can no longer optimally respond to sudden weather changes.