Manual performance during military operations in cold and windy climates is severely hampered by decreased dexterity, but valid dexterity decrease predictors based on climatic factors are scarce. Therefore, this study investigated the decrease in finger dexterity for nine combinations of ambient temperature (-20, -10 and 0°C) and wind speeds (0.2, 4 and 8 m·s2), controlled in a climatic chamber. Finger dexterity was determined by the Purdue pegboard test. Twelve subjects with average to low fat percentage were exposed to cold air for one hour with and without extra insulation by a parka. The subjects were clothed in standard work clothing of the Royal Netherlands Air Force for cold conditions. Extra insulation did affect cold sensation but not finger dexterity. The deterioration in finger dexterity depended upon Wind Chill Equivalent Temperature (WCET) and the square root of exposure time (r=0.93 for group average). A simple model is constructed that may be valuable to predict the risk for strong dexterity decrease during military operations in the cold, but more work should be done to determine critical values in dexterity for a wide variety of operational tasks.