Temperature and humidity conditions affect livestock production in Central Argentina. This study evaluates the risk of thermal stress affecting dairy production. The temperature-humidity index (THI) was used to analyze the regional and seasonal effects of temperature and humidity. Statistically, the THI was found to be normally distributed. The probability of occurrence of a daily THI higher than 72 was 40% for Río Cuarto during January. Regional variability of THI indicates a low risk of harmful extreme thermal stress conditions. The probability of THI being 78 or above ranges between 4% and 10% for the main dairy region of Córdoba during January. Also, in January and February, dairy production losses between 3 and 4 l cow(-1) day(-1) could be expected with a frequency of 5% in Río Cuarto and 15% in Villa de María de Río Seco.