Educational - Wind chill
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The wind chill affects flesh that is exposed because the flesh is heated by our circulatory system. When the wind blows, it dissipates heat from exposed flesh more rapidly than stagnant air would dissipate heat, like cooling hot foods faster by blowing on them. Since a thermometer does not generate heat, it is not affected like this.
As to why the thermometer does not already reflect this: Wind Chill is an effective temperature, meaning that a wind chill of 5 degrees when it's really 22 degrees means that the cooling (heat dissipation)effect from the 22 degree air PLUS its movement is equivalent to calm 5 degree air's cooling effect. Note that in the summer, they have a heat index, which takes into effect the humidity. Humid air reduces evaporation of moisture from flesh (sweat) and makes our bodily cooling mechanism work less efficiently.This effectively makes hot humid air FEEL hotter than hot dry air to exposed flesh. Although little is said of it, the wind chill also affects us when it's warm, and should be combined with humidity when calculating a valid heat index(though it is not done this way). If it is hot (i.e., above about 99 degrees F), wind "chill" becomes wind "heat" and windy HOT air is effectively hotter than calm hot air because it more effectively deluges us with hot air which we cannot cool with our bodies (i.e., blowing hot air on cold water heats it faster than calm hot air, hence the convection oven).
