The data presented here are the additional data used for the performance of the COSMO-CLM Mid-Holocene and Pre-Industrial simulations, used for the analysis of the manuscript of Russo et al. 2021, submitted to the journal Climate of the Past and entitled: "The long-standing dilemma of European summer temperatures at the Mid-Holocene and other considerations on learning from the past for the future using a regional climate model". The data available here are: -ext_data_044.nc: The external parameters used for the simulations, including information on soil type, albedo, land mask, etc. -W_SO_ref_half_rel_soil_moisture_18650401.nc: Soil Moisture at 50% saturation level on the first of April of the 15th year of the simulations. The data are used as reference for the simulation with different soil moisture.