The objective of the study was to determine whether the increase in the maximum temperature-humidity index (ITHmax) significantly reduced the daily milk production of cows in the intensive farms of Lima department. The study was conducted in four dairy farms over a three-year period. 8245 records of daily production of 2,488 cows were used. ITHmax was calculated using the daily records of the meteorological stations. A regression analysis was performed for daily milk production, the correlation coefficient and model determination were calculated to determine the goodness of fit of the model. We performed the analysis of variance of the regression model and estimated the regression coefficients and calculated the standardized regression coefficients. The regression model had an adjusted coefficient of determination of 34,4% and a standard error of the estimate of 7,65. Likewise, the analysis of variance of the regression indicates that the model has a high significance (P<0,001). The ITHmax regression coefficient was -0,36, being this highly significant (P<0,001). This indicates that the ITHmax significantly affects the daily milk production of the cows in Lima, and for each increase of the ITHmax, we can observe a decrease of 0,36 kg. of daily milk production.