Why do I get more static shocks in winter?
Because winter air is dry, and dry air lets electric charge build up instead of leaking away.
Static builds through contact and separation. Walking across a carpet, pulling off a jumper or sliding out of a car seat transfers electrons between surfaces, leaving one positively charged and the other negatively charged. This happens all year round.
What changes is whether the charge stays. Water is a weak conductor, and in humid air a microscopically thin film of moisture forms on most surfaces — including your skin. That film provides a continuous path for charge to dissipate gradually and harmlessly, so it never accumulates enough to jump.
Cold air holds far less water vapour than warm air. Heating that cold air indoors makes the problem worse: warming air without adding moisture drops the relative humidity sharply, and centrally heated rooms in winter can fall below 20% relative humidity, drier than many deserts. With no moisture film, charge accumulates until the voltage is high enough to ionise the air gap and discharge in a spark.
The voltages involved sound alarming — several thousand volts is typical — but the energy is tiny, which is why it stings rather than harms.
Synthetic materials make it worse because they are good insulators and sit at opposite ends of the triboelectric series from skin and wool. Natural fibres and leather-soled shoes generate less.
The practical fixes all address humidity or grounding: a humidifier, drying laundry indoors, touching a metal object with a key or knuckle rather than a fingertip, and holding the metal door frame as you get out of a car before your feet touch the ground.
Fabric conditioner works by leaving a mildly conductive residue on fibres.