Combined dendro-documentary evidence of Central European hydroclimatic springtime extremes over the last millennium

► 11,873 living and historical fir ring width samples were compiled across Europe. ► The world's largest tree-ring composite continuously spans the AD 962-2007 period. ► Tree-ring extremes were triggered by April-June precipitation anomalies. ► Documentary evidence independently confirms dendro signals over the past millennium. ► Reconstructed extremes may constrain climate model simulations over long timescales.