What do the various “apparent temperature” readings mean?
WIND CHILL takes account of how wind speed affects our perception of coldness of the air temperature. Most noticeable in shade air temperature of 10ºC or below, wind takes heat away from any insulating layer of clothing and we feel colder than in calm conditions. HEAT INDEX uses the shade air temperature and humidity readings to determine how hot we really feel. A higher humidity (water vapour content) in the air makes it more difficult for our bodies to cool by evaporating moisture through perspiration and that makes us feel less comfortable. On the other hand low humidity allows perspiration to evaporate more quickly and we feel cooler. The Heat Index reading is irrelevant below 14ºC. THW (TEMPERATURE, HUMIDITY, WIND) INDEX. This is a slightly more sophisticated calculation which incorporates the heating and/or cooling effects of the shade air temperature, humidity and wind to provide a “feels like” temperature. THSW (TEMPERATURE, HUMIDITY, SUN, WIND) INDEX. This is another more soph
