Yield is a complex trait reflecting the interaction between genotype, environment and farm management. The challenge of adapting spring crops to climate change involves unravelling the contribution of climatic factors that impact yield performance according to phenological stages. The aim of the present study was to identify the main Environmental Covariates (EC)climatic variables calculated over phenological stagesdriving spring barley yield levels. Five contrasting European agro-climatic (AC) regions were defined as follows: United Kingdom and Ireland (UK-IE), Denmark and Sweden (DK-SE), France (FR), Northeast Germany, Czech Republic and Poland (N. E. DE-CZ-PL) and South Germany and Austria (S. DE-AT). Yield data from 270 two-row spring barley accessions/varieties, grown in 125 environments between 2015 and 2021, were collected from a multienvironment trials network. Using the phenology-calibrated CERES-Barley model (DSSAT), 91 ECs were calculated in each environment based on collected weather data and simulated phenological stages. Partial Least Squares (PLS) regression analyses were carried out to sort out the main ECs impacting yield performance in each of the five AC regions. Results showed that elevated temperatures and solar radiation were the main yield-drivers in all AC regions. Associations between water availability and yield were detected in most AC regions. The strongest contrasts were observed for the critical phenological stages during pre-anthesis, which govern grain number per unit area. Cool temperatures (days with minimum temperature <0•C or <7•C and average temperature <15•C) during emergence and tillering, and solar radiation intensity between emergence and grain filling, were the most yield contributing ECs. This study showed the importance of considering climate during early stages to predict yields. The identification of major yields EC drivers suggests the need to adjust agricultural practices in spring barley production across Europe for climate adaptation. This study unraveled the complexity of yield ecophysiology affecting spring barley in Europe. In order to improve the adaptation of spring barley to climate change, the perspective is to examine the role of ECs on genotype x environment interactions for yield and develop stable cultivars that outperform existing germplasm.