"The only argument against an east wind," said the American poet James Russell Lowell, "is to put on your overcoat". Lowell was tacitly endorsing the well-known principle, very palpable in recent times, that with low temperatures the stronger the wind the colder it seems to feel.
In essence, he was talking about the "wind chill factor". Although quoted as a "temperature", wind chill as used in the media is more a measure of the influence of the wind on the perceived temperature. It is in a sense a measure of discomfort: "How cold would it have to be if there were no wind blowing, for me to feel as miserable as I do now?"
Meteorologists have always been suspicious of the notion. They see the idea as useful in the case of humans or animals in situations where they are likely to suffer adverse effects from exposure, or in studying the problem of heat-loss from buildings in winter.
Indeed, wind chill is a useful concept in any situation where warm objects are exposed in cold conditions. Put simply, in such a situation the cold wind carries the heat away. But it is quite wrong to apply the concept, as is sometimes done, to unheated, inanimate objects with no heat to lose.
The temperature of a stationary car engine, of an oil storage tank or of growing plants will not drop below the temperature of the surrounding air no matter how strongly the wind blows.
Even in the case of human beings, the extent to which we feel the cold depends on how much clothing we have on, on our age and physical condition, on whether we are physically active at the time or not, and, indeed, on whether the wind comes from behind or blows directly on to the face.
But used sensibly and appropriately, the concept of wind chill can be useful. And in an attempt to make it even more useful, and at the same time to get away from slightly confusing expression of it in terms of temperature, the World Meteorological Organisation is in the process of introducing a new measure called the Thermal Comfort Index, or TCI for short.
It will take into account the effect of humidity on our perception of excessive cold or heat, and will be expressed in terms of numbers ranging from minus 10 for bitterly cold, through zero which corresponds to the degree of comfort felt by an average person in an adequately heated living room, to plus 10 for a person subjected to a searing desert breeze.
But of this TCI, some more anon.