The objective of this study was to analyze the association between month of conception (associated with heat stress) and subsequent milk yield, fertility, and survival in cows maintained in FL dairy farms. The hypothesis was that stress conditions at conception and during the initial stages of embryonic development would have a lifetime impact on performance and survival after birth. Initial data consisted of 667,104 DHI lactation records from cows calving between 2000 and 2012 in 152 FL herds. The magnitude of heat stress in each herd was evaluated after fitting Wood’s lactation curves and comparing residuals from predicted and actual test-day milk yields by month as the direct effect of season. A sine function was fitted on the 12 residuals per farm using PROC NLIN (SAS). The difference between the highest and lowest points on the sine function was used as a seasonality index (SI). Only herds within the highest quartile for SI were included in the analyses. Cows were grouped according to the date when they were conceived: Summer (SU: Jul-Sept) and winter (WI: Dec-Feb) and comparisons were performed by parity using logistic regression and ANOVA. Control variables included calving month and year, age at first calving, and herd. Age at first calving (d) were 781 vs. 796 (P < 0.001) for WI and SU. The odds (95%CI) of survival to a second calving for WI cows were 1.19 (1.09–1.28) times the odds of survival for SU cows. Days from calving to first breeding were 138 vs. 143 (P = 0.070); 126 vs. 132 (P = 0.030); and 124 vs. 131 (P = 0.004) for WI and SU in parities 1, 2, and ≥ 3. Days to conception were 172 vs. 180 (P = 0.003); 182 vs. 187 (P = 0.070); and 179 vs. 184 (P = 0.010) for WI and SU in parities 1, 2, and ≥ 3. Milk yields (305d; kg) were 7,612 vs. 7,099 (P < 0.001); 8,011 vs. 7,665 (P < 0.001); and 7,814.6 vs. 7,532 (P < 0.001) for WI and SU in parities 1, 2, and ≥ 3. Milk yield by 70 DIM (kg) were 30.0 vs. 27.3 (P < 0.001); 35.5 vs. 33.1 (P < 0.001); and 36.8 vs. 35.2 (P < 0.001) for WI and SU in 1, 2, and ≥ 3 parity. In conclusion, cows that were conceived in the winter had better subsequent performance and survival than cows that were conceived in the summer.