The aim of the study was to measure the effect of some environmental factors in the milk production of two Holstein herds in the Chiriquí dairy basin, including milk weighing (PDC) among 1996 and 2016. The environmental temperature was obtained from two weather stations near the herds. A mixed model was applied with sire as a random effect. It was analyzed the effect of herd, age at birth, number of births, temperature and interactions among them on the PDC. The model showed differences (p <.0001) for all the effects included. The average daily production was 22.30 kg / day and 6774.05 kg accumulated at 305 days. The duration of breastfeeding was 349 ± 93 days. The effects of age at birth on daily milk production showed a pattern of sustained increases until six years of age (third birth). Herd one doubled its production while in herd two in which the increases were of the order of 40%. Two thermal zones were identified in relation to maximum temperature, first called tolerance zone where no significant effects in milk production, and another zone called thermal stress (ST) with a regression coefficient -0.268, and 42.6% of the PDC records were measured under ST conditions. It is concluded that the environmental factors evaluated affected milk production and should be considered in genetic evaluation programs for the studied area.