Bud-break and the length and depth of endodormancy (ED) were studied in grapevine (Vitis Vinifera L.) cv. Thompson Seedless (Sultana) grown in the Elqui (warm winter) and in the Maipo (temperate winter) valleys of north and central Chile, respectively. High maximum daily winter temperatures, ordinarily occurring in the Elqui valley, reduced the depth without affecting the length of ED in comparison to buds grown in the Maipo valley. Furthermore, high winter temperatures during the ED period altered the oxidative metabolism of buds by increasing its mitochondrial respiratory capacity and increasing its levels of H₂O₂. Moreover, a reduced expression in alternative oxidase transcript was also observed at the end of the ED period in buds collected from the warmer Elqui valley in relation to those collected from the temperate Maipo valley. In controlled environments, the bud-break response of ecodormant (ECD) buds depended on the climatic zones from which buds were sampled (temperate or warm winter), and on whether growth chamber temperatures were held constant or fluctuated. Mitochondrial respiratory capacity of dormant grapevine buds was raised by warmer winter temperatures, and higher subsequent H₂O₂ levels at the ECD phase appeared to be related to the erratic breaking of latent buds in subtropical areas such as the Elqui valley.