Climate change represents a continuous challenge for agriculture and world food security. A well-known characteristic of climate change is global warming, and the current knowledge on climate change highlights that temperature will be the most affected and predictable variable. Literature showed from multi-model ensembles higher increases in the frequency of warm nights compared to warm days and thereby asymmetric warming across the day is expected to continue in the future. In this context, increases in temperature, and specially night temperatures, will affect most of the crops, but specially winter crops. However, most of the studies that try to predict the effects of climate change on crops (and especially temperature) were carried under controlled condition and/or by simulation models and few were carried under field conditions. The objectives of this study were (i) to investigate the impact of high night temperatures during different period of crop cycle (i.e. critical period and grain filling) on grain yield (and its physiological and numerical components) in wheat and barley by using heating chambers placed on the crop growing in the field at 7 AM and removed at 7:00 PM every day from the third detectable stem node to 10 days post-flowering (critical period) and from 10 days post anthesis to physiological maturity (Grain filling) and (ii) to quantify and compare the impact of night temperature on wheat and barley for different representative sites of the Argentinean Pampas by modeling using APSIM by historical climatic series. Results showed that night temperature increases in the field during the critical period (ca.4°C in both crops and growing seasons) reduced yield in both wheat and barley (ca. 7% °C-1), due to reductions in grain number per unit area (ca. 6% °C1), associated with a lower number of spikes per m2. Warmer night temperatures accelerated development reducing solar radiation capture with negative consequences for biomass production without changes in Harvest index. Warmer night during grain filling reduced thousand grain weight ca. 3% °C-1causing grain yield reductions of ca. 4% °C-1 in both species. Modelling showed that wheat and barley yields declined across the Pampas between ca. 2% and 9% per °C increase in the minimum temperature during the critical period, linked to lower cumulative radiation capture as a result of a shorter crop phase and lower incident radiation due to displacement towards winter.