Climatic change has often been cited as a determining factor in cultural changes in the context of the Harappan Civilisation of northwestern South Asia, 2500-1900 BC. While these claims have been critiqued by archaeologists they continue to be accepted by non-archaeologists, including Quaternary scientists. The purpose of this paper is to assess the available evidence and published arguments and to provide a constructive working synthesis of evidence for the palaeoenvironmental setting of northwestern South Asia for the mid- to late Holocene, especially ca 4000-1000 cal BC, and its possible connection to important cultural changes. We conclude that Harappan urbanism emerged on the face of a prolonged trend towards declining rainfall. No climatic event can be blamed for a precipitous end of this civilisation, although strategic local shifts in agriculture that may have begun in response to prolonged droughts at ca 2200 BC may have contributed to the de-urbanisation process and the restructuring of human communities over the following 200-300 yr.