Pretty much everyone knows that if it’s cold outside, it will feel even colder if the wind is blowing.

But why is that?  Does it worth the same way on animals?  What about cars?  And just how do you figure out how much of the factor the wind really is?

So what is “wind chill”?  Simply put, it’s how cold you THINK it is, rather than how cold the thermometer says it is.

Here’s how it works; our bodies lose heat at a certain rate through exposed skin.  As the wind increases, the rate of heat loss increases because the wind draws heat away from the body.  That makes your skin colder which in turn results in your internal temperature dropping.  That means that not only does the wind make you feel colder, you ARE colder.

How much colder?

Let’s say that the air temperature is -10 C and the wind is blowing at about 15 km/h.  You will think it’s actually closer -20 C.  That’s the wind chill temperature.  Keep in mind, this is on exposed skin.  So, the better you’re covered, the less of an effect the wind will have on you.

Here’s a link to the US National Weather Service’s Windchill Chart.  The chart is in Fahrenheit and uses MPH for speed.  However, at the bottom of the page there is an actually calculator where you can use either Fahrenheit or Celsius and either MPH or KM/H.

Or if you like, you can figure out for yourself.  Here’s the formula:

T_wc = 13.112 + 0.6215 T_a -11.37 V^0.16 + 0.3965 T_a V^0.16 where T_wc is the wind chill, V is in the wind speed in kilometres per hour, and T_a is the ambient air temperature in degrees Celsius.

Wind chill also affects animals, although not to the same degree.  With much less exposed sin, they do have better protection.  However, it will make them feel colder.  This is especially true for very young and very old animals.  Same is true for very young and very old humans.

The wind chill does NOT affect inanimate objects.  It can make something like a car’s engine cool down faster than it would if the wind was calm.  However, it can’t cool the engine below the air temperature.

Wind chill plays an important role in determining how quickly someone could develop frostbite or hypothermia.  Whilst those two conditions aren’t as likely to affect someone in New Zealand as they are likely to affect someone in say, the United States, the Wind Chill Factor is still an important tool here.  You need to make sure you dress for the wind chill temperature and protect your animals based on the wind chill temperature, not the air temperature.

Because the bottom line is; the wind chill temperature is the only temperature your body (and your animals’ bodies) care about.

Homepage image /Jessica Double

By WeatherWatch Analyst Howard Joseph