The aim of this experiment was to evaluate the continuous collection of vaginal temperature for 72 h (every 10 min) in lactating Holstein cows (n = 480; 591 data collections) allocated in one single cross-ventilation barn. Cows were fitted with a thermometer attached to a progesterone intravaginal device before AI. Milk production, DIM, skin thickness, coat color, body condition score (BCS), and pregnancy per AI (P/AI) data were collected and recorded for further analyses. Ambient temperature and humidity was measured for 72 h using a data logger for calculation of the temperature and humidity index (THI). Data were analyzed using ANOVA and Pearson correlations using proc GLM, Corr and Logistic of SAS. Maximum THI (MAX) and percentage of time above a vaginal temperature of 39°C (PCT) were used as data logger responses, class variables were created for MAX and PCT (High vs Low) using the median threshold. There was a low correlation between THI and PCT (r = 0.01). Skin thickness was also poorly correlated with PCT (r <0.01). Cows with black color coat spent less time with high vaginal temperatures (P = 0.05). Primiparous (P = 0.04) and cows with low BCS (P < 0.01) had greater PCT. Milk production was affected by parity (P < 0.01) and PCT (P = 0.02; High = 43.5 vs Low = 41.2 kg/d). There was a milk production by MAX interaction for PCT (P < 0.01), whereas only cows in the highest milk production quartile (>50.7kg/d) spent more time with high vaginal temperatures. Among the independent variables included in the model, parity (P < 0.01), PCT (P = 0.03; 26.1 vs 17.4% for Low and High, respectively) and a PCT by milk production interaction (P = 0.05) affected P/AI. The decrease in P/AI in cows with High PCT only occurred in cows with the highest production. In summary, there is a large variability on how individual cows respond to heat stress. Parity, BCS, coat color and milk production affect PCT, particularly under high ambient temperatures. Selection of animals with efficient control of body temperature in spite of high milk production should be further approached as a strategy to maintain adequate fertility.