How does wind cause the temperature to feel colder?
When you are sitting in front of a fan on a hot day, the blades of the fan propel air molecules toward you, speeding them up and smacking them against your skin [1]. The explanation for why this feels cool lies in the fact that there are two types of motion on the atomic scale [1]. One feels hot, and the other feels cold [1]. When atoms and molecules are jiggling really rapidly in random directions, they feel hot against our skin [1]. However, the collective motion of all the atoms and molecules in a single direction doesn't affect their overall temperature [1]. When the wind blows, it removes that layer of warmer air near our bodies [2]. This speeds up heat loss, so it feels much colder than it really is [2].
It can feel colder when the wind is blowing, because the wind helps remove the warm air next to the skin and this causes a feeling of it being colder [1]. The temperature of the air does not change, but the wind chill was developed because of the feeling that it gets colder when the wind is stronger due to a more rapid heat loss from the body [1]. Windy conditions can cause the body to cool off faster and this can lead to health impacts such as hypothermia [1]. When the wind increases, it draws heat from the body, driving down skin temperature and eventually the internal body temperature [3].