Where did wind chill factors come from?

Part of a continuing weekly series on Alaska history by local historian David Reamer. Have a question about Anchorage or Alaska history or an idea for a future article? Go to the form at the bottom of this story.

In “Travels with Charley: In Search of America,” John Steinbeck wrote, “What good is the warmth of summer, without the cold of winter to give it sweetness.” While true, Steinbeck lacked experience in a place like Alaska, let alone the Antarctic. What did the great author know of the cold combined with wind, of the wind chill factor beyond mere low temperatures?

During Admiral Richard Byrd’s 1933 to 1935 second expedition seeking the South Pole, a participant noted, “the real agony of the cold comes from the wind,” as “like a knife drawn across the face.” At some level, everyone understands wind chill, how exposed skin loses heat more rapidly on a windy, cold day than on a still one. The concept is simple and present throughout documented history, but the calculations are a bit more complicated. In this way, the current understanding of wind chill, with charts and factors, is a surprisingly modern concept, only entering the public space a couple of generations ago.

Paul Siple (1908-1968) coined the term “wind chill” in an unpublished 1939 dissertation that included the first formula for a wind chill index. Again, the idea behind the idea was old. In a 2021 journal article, researchers Harvey Lankford and Leslie Fox noted 89 studies and experiments along similar lines published and conducted between 1912 and 1941. Yet, Siple was the experienced innovator.

More than perhaps any American in history, outside your average Utqiaġvik resident, Siple knew about extreme cold. He was still a teenager when selected from more than 800,000 other Boy Scouts to accompany Byrd’s First Antarctic Expedition of 1928-30. There may not now be a law preventing polar expeditions from drafting Boy Scouts, but perhaps there should be. Siple scraped barnacles, loaded coal, scrubbed decks, and hunted penguins. He was an occasional helmsman and amateur taxidermist, still chronologically a youth when Byrd described him as “a man among men.”

After accompanying Byrd’s Second Antarctic Expedition, Siple earned a doctorate in geography and climatology, then returned to Antarctica as leader of the Little America III research station from 1939 to 1941. His research there captured the attention of the Army, prompting a lengthy partnership with the American military and, in 1956, the inaugural scientific leadership of the Amundsen-Scott Station. Across six trips due south, he spent 10 summers and four winters in the Antarctic.

Also at Little America III was Charles Passel (1915-2002), a sedimentary paleontologist with a surprising amount of free time on his hands. As they wrote in the resultant study, published in 1945, “Perhaps there is no place on earth where one is so acutely aware of need for a suitable scale to express sensible temperatures as the polar regions. Here there is striking contrast between relatively tolerable days of calm, subzero weather, and windy days that are warmer although sensibly much more unpleasant.”

Building off his unpublished 1939 dissertation, Siple devised an experiment to define human comfort in different frigid conditions. He wrote, “I set up an experiment to try to measure the rate in time it took a small cylinder of water to freeze. Charlie Passel helped me measure accurately the exact length of time that the cylinder remained at the freezing point while it was letting up its heat of crystallization under nearly 100 different combinations of wind, velocity and temperature.” In other words, they left a little handmade plastic water bottle on a stick outside and regularly checked in to see how it was doing.

Siple and Passel published the results in 1945, including a wind chill chart, though not in any form a layperson from today would recognize. The Siple-Passel chart offered a range of values from 0 to 2600 with descriptive notations. For example, the chart noted “nude sun-bathing possible” at 100, “travel and living in temporary shelter becomes dangerous” at 2000, and “exposed areas of face will freeze within less than 1/2 minute” at 2600. Siple would later record a reading of 3290 at the South Pole, which he interpreted as “little chance for lengthy survival.” From nude sunbathing to death, the science hippies think of everything.

Though crude in methodology and analysis, the Siple-Passel index became a wind chill benchmark. All subsequent wind chill research and formulas build upon, adapt, praise, critique, refute, or at least acknowledge Siple’s rough experiment in some way. For as much tinkering as there would be with its underlying mathematics, the most crucial subsequent innovation in wind chill science was its presentation. The Siple-Passel index was simply not intuitive. As regards the cold, the public tends to think in terms of temperature readings on a much shorter scale than 0 to beyond 3,000. In 1961, the Army adapted the Siple-Passel index into a chart that converted the wind chill effect into a recognizable temperature. A 1965 Air Force study produced a different wind chill temperature chart, one that was printed onto small cards for service members.

Through the 1940s, 1950s, and 1960s, the idea of a calculated “wind chill” effect was almost solely the domain of the military and scientists. Even in Alaska, the idea of a specific “wind chill temperature” was practically non-existent in the public sphere until the 1970s, when meteorologists adopted the concept. Per a report by the U.S. Office of the Federal Coordinator of Meteorological Service, National Weather Service meteorologists began using wind chill temperatures in 1973.

As for the public, the effect was sudden. From 1946 to 1992, Anchorage had two major newspapers, the Daily Times and the Daily News, the latter the winner of what some call the last great newspaper war. During the 1950s and 1960s, the two newspapers used the terms “wind chill” or “windchill” a combined 22 times. But during the 1970s and 1980s, the two newspapers employed those terms 2,329 times.

As for Alaskans themselves, the term became part of our arsenal, another descriptive term to include in our winter weather tales. For example, during a 1972 Daily Times interview, longtime Alaska Railroad engineer Bill Stewart regaled readers with tales of extreme weather. “There have been times when the snow drifts by Summit Lake have been over ten feet,” said Stewart. “The train stopped one time when the wind chill factor was minus 100. We had to wait almost a day before help got to us, but we usually don’t have to worry about the drifting.”

Key sources:

Allen, Cathy. “Chugging Through the Alaska Bush.” Anchorage Daily Times, November 25, 1972, 2A, 4A.

Lankford, Harvey V., and Leslie R. Fox. “The Wind-Chill Index.” Wilderness & Environmental Medicine 32, no. 3 (2021): 392-399.

Osczevski, Randall J. “The Basis of Wind Chill.” Arctic 48, no. 4 (1995): 372-382.

Siple, Paul A., and Charles F. Passel. “Measurements of dry atmospheric cooling in subfreezing temperatures.” Proceedings of the American Philosophical Society 89, no. 1 (1945): 177-199.

Wilson, Leonard S. “Paul Allman Siple, 1908-1968).” Annals of the Association of American Geographers 59, no. 4 (1969): 815-819.