Temperatures below 0°C during spring is a restrictive factor for the production in temperate zone for fruit species with early budbreak. Temperatures below -2°C during the first grapevine developing leaves, results in a significant loss of yield for that season. The SIS - Selective Inverted Sink - operates during nights with radiation frosts, by selectively extracting the cold air. Due to its higher density, cold air locates in lower layers, closer to the ground and when the SIS extracts the said lower layers this allows the hottest air from the higher layers, to reach the crop. The objective of this research was to evaluate the space and time temperature distribution during radiation frost nights with and without cold air drain by the SIS. The temperature during these nights in low vineyard areas shows the influence of SIS operation. Once the cold air started to be drained the valley temperature initiated to increase to reach high temperatures. The SIS system increased the temperature with 2°C in zones with high frost risk in vineyards of the Napa Valley, California, USA and Alto Valle, Rio Negro, Argentina. The modification of the crop microclimate and the agronomic significance of the increased temperatures is discussed.