The wind chill factor is a measure of how cold it feels to humans due to the combined effects of temperature and wind speed, and it is not directly measurable by conventional mercury thermometers. Wind chill only applies to living beings, as humans experience evaporative cooling and heat loss, making them feel colder than the actual air temperature. Different wind chill scales exist, such as those used by the Navy, US, and Canada, leading to some confusion in temperature perception over time. Humans differ from thermometers in that they generate heat and can be insulated by a layer of air, which wind can disrupt. Understanding these differences is crucial for accurately assessing cold weather conditions.