Objective. Determine the effect of some variation factors that affect the characteristics of birth weight (BW), adjusted weaning weight (AWW) at 90 days and pre-weaning weight gain (PWW) in Colombian hair sheep. Materials and methods. 525 data from Colombian hair sheep (OPC) offspring, reared in an extensive production system under conditions of the lower Colombian tropics were used. A linear fixed effects model (GLM) was used, which included the sex of the calf, the type of calving (single or multiple), the calving number of the ewe (primiparous or multiparous), the climatic season of birth (dry or rainy) and the year of birth (2017 to 2020) and their interactions. The analyzes were carried out with the statistical package SAS University, 2021®. Results. The BW, AWW and PWW values were 2.9±0.1 Kg, 13.2±1.6 Kg and 0.15±0.064 Kg, respectively. The BW was significantly affected (p <0.05) by all the factors studied. So then, the males, the offspring of simple delivery, of first-time ewes, in the rainy weather season and in 2019 had better performance. The AWW only varied significantly due to the effects of calving number, the climatic season and the year. Finally, the PWW was only affected by the rainy weather season and by the year. Conclusions. The BW turned out to be the variable most sensitive to the factors analyzed. In maternal effects, the type of delivery did not affect the AWW and PWW, while the number of deliveries affected the AWW but not the PWW.