|VALUE OF THE WIND CHILL INDEX
METEOROLOGIST JEFF HABY
The wind chill index can give a person a relative sense of how cold it will feel to exposed skin outside. The
colder the wind chill index, the colder it will feel (all else being equal). The wind chill index is a good
tool to warn the public of the dangers of frostbite and other potential negative health effects from very cold
1. The wind chill index is extremely time variant. The value of the wind chill index varies moment to moment.
As you know the wind speed is not constant. In the
boundary layer the wind blows in gusts and turbulence
causes variations in wind speed moment to moment. The primary factor (besides temperature) that goes into
the wind chill equation is wind speed. Since wind speed fluctuates significantly from moment to moment,
the wind chill index will do the same.
2. Wind chill is not very relevant when a location is experiencing typical weather. Generally, the wind chill
is most relevant when an anomalously cold air mass effects a region. People adapt to the environment in
which they live. People generally understand how to dress and prepare for their "climate".
3. The wind chill can not account for several other factors that contribute to how a person feels. It is okay
that it does not account for these other factors since each of these factors will vary from person to person.
As mentioned, the most important factor besides temperature is the wind speed. The wind speed changing from
moment to moment will overpower many of the secondary factors that contribute to how a person feels anyway.
It is good that the wind chill remain simply an index based on temperature and wind speed. Some of the
secondary factors that effect how a person feels include: exposure to sunlight, whether skin is wet or dry,
clothing, body type, hair growth, and metabolism. See Haby hint below on 6 factors that affect
how a person feels:
As mentioned many of these secondary factors change moment to moment and/or vary from person to person. If
sunlight is factored into equation, that will vary from person to person and moment to moment since people
tend to walk in both shaded and sunlit areas when they walk outside. People have varying body types, hair
growth and metabolism. If it is raining and cold, some people may get wet while others will not.
4. The wind chill temperature does not mean that objects can cool to the wind chill temperature. Objects
can only cool to the actual temperature of the air. The wind chill index is based upon the rate of heat loss and not
on how the wind changes the temperature of objects.