Wind chill: Its history & effect on people & things
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He said to the TV reporter: "...with the high winds and the wind chill factor, I'm servicing many more cars than usual due to dead batteries." "He" was a tow truck driver helping a driver get her car started during a recent cold spell. After watching that exchange, I was prompted to write this article.
Was he right? Do batteries really weaken or go dead more easily when there is a very strong wind chill factor? The larger question really is whether the wind chill factor affects inanimate objects at all.
A little history first. In 1945, Antarctic explorers Paul Siple and Charles Passel devised an index that attempted to compare how cold we feel at various temperatures and wind speeds with how cold we feel at the same temperatures in still air. This original wind chill index languished, more or less, until it gained great notoriety during the famous (or infamous) "Ice Bowl" Championship Game between the Dallas Cowboys and the Green Bay Packers in Green Bay in 1967. With a game-time temperature of -13F and a wind chill factor of -48F (according to the original index), it was one of the two coldest pro football outings ever staged. (The other was the 1981 AFC Championship Game between the San Diego Chargers and the Cincinnati Bengals, which was played in -9F weather with a wind chill of -59F (original index).
Since those games, the wind chill index has been revised at least once to reflect the fact that the National Weather Service believes we don't feel as cold under wicked winter winds as previously thought. (The earlier game is now considered to have been played in a -36F wind chill, and the 1981 game in a -37F wind chill -- still not exactly a walk in the park.)
Although the wind chill index has been relaxed, the media has not relaxed (in my humble opinion) its overemphasis of it -- almost to the exclusion of the actual air temperature. I suppose it sounds much more dramatic to say that it feels like 17F when it's really 35F. Furthermore, since there are several mitigating factors that lessen the impact of the wind chill factor -- e.g., warm clothing, sunshine, etc. -- the actual index should only be used as a rough guide anyway.
By the way, I believe the wind chill factor was zero on Super Bowl Sunday at Miami's Dolphin Stadium. That's zero as in no wind chill factor, as the high temperature was 66F and I saw no reports of frostbite. (The average high in Miami for the date is 77F.)
So what about the wind chill factor's effect on inanimate objects? It turns out there is none, unless you consider the following as an "effect": Wind will cause an exposed warm machine, such as a car engine, to cool more rapidly (down to the ambient air temperature) once shut off, and once turned back on, the engine will take longer to reach normal operating temperature. Although not a heating engineer, I'm told this is because in both instances, heat is removed more rapidly than otherwise would be the case.
As for your car's radiator, obviously follow the manufacturer's recommendations, but as long as the air temperature is above freezing, the radiator mixture won't freeze anyway, no matter how low the wind chill factor gets. And that car battery?... yes, it's more difficult for the battery to start the engine in cold weather because of a slower chemical reaction (thus the importance of cold cranking amps), but the wind chill is irrelevant.
However, if one were to park a car outside under severe wind chill conditions and return to the car, say, in two hours, I suppose the battery would have cooled down to the air temperature more quickly than otherwise, making it more difficult to start with a weak battery.
Above all, please don't risk frostbite by going unprotected, especially when temperatures and winds combine for frostbite times of 30 minutes or less,, as showin the wind chill chart at the top of this post. I know our colleague, Ann Posegate, who recently spent time in Antarctica, was well protected, as she says she was wearing 24 pounds of wool, polar fleece, polypropylene, leather and plastic -- and it's summer in Antarctica!
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