Drier conditions tend to result in a higher risk of static electricity buildup, which can lead to electrostatic discharges. This is due to the fact that the air moisture content is a natural conductor, earthing any potential static charge.
@Thandeka If it's freezing outside and you are heating then air can get very dry indoors. The driest air I ever experienced was in winter when it was around -10°C outside and the heating was on at home. It usually gets that bad that my hair raises up.