The temperature reported by a thermometer often fails to capture how a person actually perceives the weather outdoors. This leads to confusion between the specific meteorological term “wind chill” and the general term “feels like” temperature. While these two concepts are closely related, they are not always interchangeable. Understanding the science behind each metric helps interpret a weather forecast accurately.
The Science of Wind Chill
Wind chill is a specialized metric calculated only when air temperatures are cold, typically at or below 50°F (10°C), and wind speeds are noticeable. It measures the rate of heat loss from exposed skin, not a change in the actual air temperature itself. The human body naturally creates a thin insulating layer of warm air next to the skin, known as the boundary layer.
Moving air constantly strips this warm boundary layer away, exposing the skin to the colder ambient air more quickly. This process, known as convection, accelerates the rate at which the body loses heat. The calculation uses the actual air temperature and the wind speed measured at five feet, approximating the height of an adult’s face. The resulting number indicates what the air feels like on exposed skin due to the combined effect of cold air and wind.
The wind chill value represents the temperature that would result in the same rate of heat loss if the air were calm. For instance, an air temperature of 20°F with a 15 mph wind creates a wind chill of 6°F. Forecasters use this metric to communicate the risk of cold-related injuries, as lower wind chill temperatures correspond to a faster potential onset of frostbite. The wind chill factor does not cause inanimate objects to cool below the actual air temperature.
The Broader “Feels Like” Temperature
The “feels like” temperature, also known as apparent temperature, is the overarching term used by weather services to provide a single, relatable number for comfort. This metric is dynamic and is reported year-round, unlike wind chill, which is strictly seasonal. During warm weather, the dominant factor influencing the “feels like” temperature is the Heat Index.
The Heat Index incorporates relative humidity into the calculation. High humidity affects the body’s ability to cool itself because sweat evaporates slowly when the air is saturated with moisture. This causes the body to retain heat and feel much hotter than the thermometer reads. When temperatures are moderate, falling between the thresholds for wind chill and the heat index, the “feels like” value is often the same as the actual air temperature. The “feels like” temperature adopts the most relevant index for the current conditions.
Distinguishing the Two Terms in Practice
The primary distinction is that wind chill is a specific index, whereas “feels like” is a general reporting term that utilizes various indices. When conditions are cold and windy, the wind chill calculation becomes the “feels like” temperature. In this scenario, the two numbers are identical because wind chill is the only significant factor influencing the perceived temperature.
Conversely, on a hot and humid day, wind chill is not calculated, and the “feels like” temperature is determined by the Heat Index. If the air temperature is 90°F with high humidity, the “feels like” temperature might rise to 105°F, a value driven entirely by moisture, not wind. Therefore, wind chill is only one of the major calculations that the broader “feels like” term uses to communicate how the weather truly affects the human body.