This study aimed to determine the effect of heat stress on milk losses by calculating the temperature-humidityindex (THI) of the districts of Şanlıurfa. The data set of the research comprised meteorological data belonging to 10 districtsof Şanlıurfa province between 1999-2019, which were got from Diyarbakır Regional Directorate of Meteorology and thenumerical values of the dairy cows in the year 2019 were provided by the Turkey Statistical Institute (TUİK). In the study,THI values between May and September, geographic areal distribution of the THI value, daily milk losses per cow, and dailytotal milk losses in all districts of the province were determined. In the study, when the months and districts where THIvalues exceed the critical values were considered, the district with the highest daily milk loss per cow because of high THIvalues was determined as Şanlıurfa center with 10.828 g in August and the lowest was determined as Hilvan with 163 g inJune. Thus, it was determined that milk losses because of THI were mostly in July and August and the most affected districtswere Şanlıurfa Center and Akçakale. Also, the district with the highest average daily milk losses obtained by using the totalnumber of dairy cows over 2 years old in Şanlıurfa provinces and districts got from TUIK was determined as Siverek inAugust with 27283 kg, and the district with the lowest was determined as Bozova with 71 kg in June. The districts with thehighest losses during the months in question were Şanlıurfa Center, Akçakale and Siverek, depending on the dairy cowpopulation. As a result, it was determined that Şanlıurfa dairy enterprises experienced significant milk yield losses due toheat stress, especially in July and August. It will be beneficial to improve maintenance-management practices duringperiods of high environmental temperature to prevent heat stress and milk loss.