This has to do with the moisture content of the air. Moisture in the air reduces the buildup and promotes the discharge of accumulated static charge.
Colder air has less ability to retain moisture as the lower thermal energy allows condensation to take place more readily. Heating cold dry air further reduces the relative humidity of the air increasing its ability to draw moisture from its surroundings.
Charges tend to seek equilibrium. One way to achieve this equilibrium is to align the charges in an orderly equal distribution . . . like this -
https://www.google.com/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=static+hair+images