Why do you get shocked by static electricity more in winter?

Static charge accumulates whenever two dissimilar materials rub and separate, transferring electrons: your shoes on carpet, a wool sweater over a shirt, sliding across a car seat. Your body holds that charge until it finds a path to ground. In humid air, a thin film of water on surfaces and the moisture in the air itself conduct well enough that charge dissipates continuously and never builds to a noticeable level. In dry air it has nowhere to go, so it accumulates to thousands of volts and discharges in a spark when you approach a conductor. The current is tiny, which is why it stings rather than injures.

Winter produces the conditions. Cold air holds little moisture, and heating it indoors without adding water drops relative humidity into the 10 to 20 percent range, drier than many deserts. That is why static shocks, flyaway hair, and clinging clothes all arrive together in the same season and vanish in summer.

Practical fixes follow from the mechanism. Raising indoor humidity to around 40 percent with a humidifier is the most effective, and it also helps skin, sinuses, and wood furniture. Leather-soled shoes conduct better than rubber; natural fibers generate less charge than synthetics; and touching a doorknob with a key or a knuckle first spreads the discharge over a less sensitive point. Dryer sheets and anti-static sprays work by leaving a conductive residue. The same physics is a genuine hazard in fueling and electronics, which is why gas pumps warn against re-entering the vehicle mid-fill and why computer components are handled with grounding straps.