The primary function of a ceiling fan, in any season, is to circulate air throughout your room. While this does not really cool the air, it can help a room feel more comfortable as warm or cold air will no longer be stationary. During the summer months, you should set your fan to rotate counter-clockwise. This will push the air downwards and create a windchill effect as it brushed by you. During the winter months, set your fan to rotate clockwise. This will pull air upwards, displacing the warmer air that settles near the ceiling, as heat rises. Simply redistributing and keeping the air in movement can make a great difference.