Well the basics are that the prevailing winds in the winter are coming out of the North West on the North American Continent.Also known as Artic blasts. However, on some odd occasions the jet stream swings around and a high preasure system slips in and changes the whole works. This is why I set up my main stands on the southeast side of a field or corridor, but always have a backup on the other side of the field or lane. Along with a way to get in and out without crossing the shooting zone.