The endodormancy is the tree inability to restart budbreak even with moderate temperatures. Meanwhile in the ecodormancy the lack of budbreak is observed only when temperatures are not favorable for growing. Both, the chill and the heat, have cumulative effect. They are measured in modified Utah Chill Units (UFUM) and Growing Degree Centigrade Hours (GDHºC) respectively. The ecodormancy beginning allows setting up the GDHºC requirements. This study was carried out in two locations and during three years. The objective was: to determine the endodormancy chilling requirements and ecodormancy chilling and heat necessities. It was observed that with more than 677 UFUM the buds of “Bing” variety were sensitive to middle amount of heat. The UFUM and GDHºC effect on budbreak follows the Arrhenius law. The double exponential mathematical model selected explains conveniently the heat-cold effect on budbreak. It also allows determining when vegetative tissue begins to be sensitive to chemical products that replaces chill unit and allow assessing their effects with a more solid ecophysiological base.