Climates inferred from former glacier geometries in some areas exhibit discrepancies with regional palaeoclimates predicted by General Circulation Models (GCMs) and modelling of palaeoecological data, possibly as a consequence of their differing treatments of climatic seasonality. Since glacier-based climate reconstructions potentially offer an important tool in the calibration of GCMs, which themselves need validation if used to predict future climate scenarios, we attempt to resolve mismatches between these techniques by (1) investigating the influence of seasonality on glacier mass balance, and (2) refining the methodology used for the derivation of glacier-based palaeoclimates. Focussing on the Younger Dryas stadial glaciation of Scotland, northeast Atlantic, we show that sea-ice amplified seasonality led to a significantly drier climate than has been suggested by glacier-based interpretations. This was characterised by a relatively short ablation season and the survival of a more substantial winter snowpack. We suggest that if palaeoglaciological studies were to account for changes in seasonal temperature and precipitation variability, their results would agree more closely with the cold, arid, northeast Atlantic palaeoenvironment predicted by atmospheric modelling and northwest European pollen studies, and would therefore provide more accurate constraints for GCM calibration.