The Wind-Chill Index

This Lessons from History article about the wind-chill index (WCI) explores the historical polar and meteorologic literature relevant to the topic and presents unpublished work from 1939. Geographer Paul Siple (1908–1968) was a 6-time Antarctic explorer and scientist who invented and named the WCI in his doctoral dissertation at Clark University. Siple and Charles Passel (1915–2002) performed studies in Antarctica in 1940 that led to publication in 1945. This paper is often credited as the beginning of the WCI. Through years of critiques and revisions by others, these efforts evolved into the wind-chill equivalent temperatures (WCTs) used today. This essay explores the history, the science, and the overlooked originality, simplicity, and details of Siple’s unpublished work. The remarkable similarity of the original chart to a current chart is shown by adapting and overlaying the 1939 WCI onto a current WCT chart with its times-to-frostbite data. The writings of Siple, Passel, and others provide an evocative supporting narrative to illustrate some of the problems of living in cold environmental conditions.