Желдің салқындату әсері немесе "желдің суықтығы" құбылысы

Lowering of body temperature due to the passing flow of lower temperature air
the meteorological effect of "wind chill"

Wind chill (popularly wind chill factor) is the sensation of cold produced by the wind for a given ambient air temperature on exposed skin as the air motion accelerates the rate of heat transfer from the body to the surrounding atmosphere. Its values are always lower than the air temperature in the range where the formula is valid. When the apparent temperature is higher than the air temperature, the heat index is used instead.

A surface loses heat through conduction, evaporation, convection, and radiation. The rate of convection depends on both the difference in temperature between the surface and the fluid surrounding it and the velocity of that fluid with respect to the surface. As convection from a warm surface heats the air around it, an insulating boundary layer of warm air forms against the surface. Moving air disrupts this boundary layer, or epiclimate, carrying the warm air away, thereby allowing cooler air to replace the warm air against the surface and increasing the temperature difference in the boundary layer. The faster the wind speed, the more readily the surface cools.

Many formulas exist for wind chill because, unlike temperature, wind chill has no universally agreed upon standard definition or measurement. All the formulas attempt to qualitatively predict the effect of wind on the temperature humans perceive. Weather services in different countries use standards unique to their country or region; for example, the U. S. and Canadian weather services use a model accepted by the National Weather Service. That model has evolved over time. The first wind chill formulas and tables were developed by Paul Allman Siple and Charles F. Passel working in the Antarctic before the Second World War, and were made available by the National Weather Service by the 1970s. realized that people are rarely still and that even when it is calm, there is some air movement. He redefined the absence of wind to be an air speed of , which was about as low a wind speed as a cup anemometer could measure. This led to more realistic (warmer sounding) values of equivalent temperature.