Sand dunes on the Newnes Plateau (1000 m a.s.l.), west of Sydney, were active during the Last Glacial Maximum. The scattered sand dunes are forested under the modern humid, temperate climate regime. Dune types range from parabolic to transverse lee dunes and sand sheets or patches. All point to the presence of conditions marginal for aeolian activity, made possible through wind acceleration on windward slopes, ready sand supply from the weathered sandstone of the plateau and sparse vegetation cover. Modern climate envelopes of sand dune activity in Australia predict that unrealistically drier conditions are necessary to allow wind transport at this site. Only additional impediments to plant growth, such as lower temperature and lower atmospheric carbon dioxide concentrations, appear to allow the necessary conditions for dune formation. These observations and conclusions extend our understanding of the extremes of the LGM climate in humid eastern Australia, confirming that the widespread treeless vegetation was also sparse, even in areas that today have annual rainfall above 1000 mm.