Under seasonal change in milk production we can find large number of factors of which the most important are mentioned in this article. Most of the seasonal changes are associated directly or indirectly with the temperature and humidity and that is why we devoted most of the time to these factors. Thus, the changes in feeding during different periods can be correlated with changes in temperature, because animals tries to maintain a normal body temperature, so the energy that is normaly used in metabolic purposes now is exploited for the purpose of thermoregulation, which is reflected in the reduction of food intake. That is why in different periods we alter the composition of servings of dairy cows in order to ensure sufficient energy supplies to more easily maintain normal body temperature while maintaining the highest possible daily milk production. In this work we have done research of the direct influence of temperature humidity index and thermal stress on the daily quantity of milk production, somatic cells in milk, percentages of milk fat and total dry matter without fat in the milk of dairy cows on the farm Grube d.o.o. Potnjani. We also mentioned the influences of heat stress on many other physiological factors. We also analyzed the influence of the season in which the cows calved, which according to many research has a significant impact on the production of milk. At the end of the work we mention the ways of protection which can reduce the effects of seasonal changes in order to maintain the quantity and quality of milk production at a high level.