Climate change is an urgent global issue that necessitates a comprehensive understanding of past, present and future climate. To understand current human-induced climate variability and predict future conditions, past climate reconstructions are crucial. Tree rings are recognised as natural archives of past growing conditions, and are commonly used for reconstructing past climate, although they have proven to be a less robust proxy in temperate regions. Stable oxygen isotopic ratios in tree-ring cellulose have been validated as a sensitive hydrological proxy, also under temperate climate conditions. This PhD proposal aims to reconstruct summer precipitation in Flanders from 1100-1600 CE using stable oxygen isotopes in oak tree rings as a proxy. The many well-preserved historical timber constructions in Flanders allow to build an isotope master chronology. Tree-ring-dated historical timbers provide ample material for isotope analysis and to unlock their so far unexplored value as archives of past climate. The project aims to calibrate and verify the climate signal in annually resolved oxygen isotope series from living oaks and subsequently reconstruct summer rainfall based on the master chronology. This will allow to assess precipitation patterns and drought events over the medieval period, thereby addressing spatial and temporal gaps in climate reconstructions, contributing to a better understanding of historical climate conditions in Flanders and on a regional scale.