What cold weather does to a watch
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Cold weather rarely harms a watch in good order, and most of what it does passes once the watch is warm again: a mechanical watch may run a little off its usual rate, a quartz battery delivers its power less readily, and a digital display can turn sluggish. The lasting risk is moisture. Coming in from the cold can expose a seal that no longer holds, and mist that stays under the crystal needs a watchmaker promptly. Kept on the wrist under a cuff, a sound watch comes through a Canadian winter well.
Where the cold matters
What counts is the temperature of the watch, not of the air. On the wrist, under a sleeve, a watch stays close to skin temperature even on the coldest days. It gets truly cold only away from the skin: overnight in a parked car, which by morning is about as cold as the air outside, in an outer coat pocket, or strapped over a ski jacket for a day on the hill. In its advice on the accuracy of mechanical watches, Seiko recommends against leaving one where the temperature is below 5 °C or above 35 °C. Its general care advice adds that operating temperature ranges differ from calibre to calibre, and refers owners to the instructions for their own.
Mechanical watches in the cold
Two things change as a mechanical movement cools. Its metal parts, the balance and its spring among them, contract slightly, and Seiko notes that a mechanical watch tends to gain time in the cold and lose it in the heat. Modern balance springs are made of alloys chosen to keep that effect small, but no movement is free of it: COSC tests chronometer movements at 8, 23 and 38 °C, and how far the rate varies with temperature is one of its criteria.
The oils also thicken as they cool, adding friction throughout the movement, so the balance swings through a smaller arc and the rate shifts with it. In a watch serviced on time and worn on the wrist, the effect is slight. In one overdue for service, whose oils have already thickened and spread with age, the drag of deep cold can make it run erratically or stop, and that may be the first sign that a service is due.
Neither change lasts. Back at room temperature the rate returns to normal, though any seconds gained or lost while cold stay on the dial until the watch is set. A watch that still misbehaves when warm has a fault the cold only revealed. A sudden large gain points to magnetism rather than the cold, as why a mechanical watch runs fast explains, and a watch that is irregular or stops even indoors needs the full service described in when a watch needs an overhaul.
Quartz watches in the cold
A quartz watch is far less affected, but not untouched. Its quartz oscillator vibrates 32,768 times a second, and that frequency shifts a little with temperature, so a watch left in the cold can run slightly off until it warms. High-accuracy movements, rated to about ±10 seconds a year, are thermocompensated: they measure their own temperature and correct for it, as choosing between quartz and mechanical explains.
The battery feels the cold more than the oscillator does. A cold cell delivers its power less readily, and recovers as it warms. A fresh battery copes. One near the end of its life may not: in the cold it can bring on the watch’s low-battery signal early, or stop the watch. On many analogue quartz watches that signal is a seconds hand moving in two-second steps. Once the signal has appeared, the battery is due, even if the watch seems normal again indoors, and it is best replaced soon, since a spent cell left in a watch can leak and corrode the movement.
A digital display can be slow to change in freezing weather, because liquid crystal responds more slowly in the cold; it is not a fault, and the display recovers as the watch warms. A solar-powered watch can run short of charge: Seiko and Citizen both point out that it charges less in winter, when the sun is low and the watch spends the day under a sleeve, and Seiko suggests five or six hours by a window, dial to the sun, once a month.
Moisture, the lasting risk
Moisture does its harm on the return to warmth rather than in the cold itself. A watch is sealed by gaskets of rubber and plastics at the case back, crown, crystal and any pushers. These stiffen in the cold and harden with age, and an old gasket that has taken a set presses less firmly on its seat. A cold watch carried into a warm room collects condensation from the air. On the outside of the glass that is harmless and wipes away. If a seal is no longer sound, moisture can also get into the case and condense on the inside of the still-cold crystal.
Dry the glass, then wait. Citizen’s guidance on a fogged crystal is that fog which disappears within a couple of minutes of drying the glass is no problem, while fog that stays may mean a fault in the water sealing. Mist that stays under the crystal, droplets, or rust spots on the dial or hands mean moisture is inside the case. Stop wearing the watch and have it opened and dried promptly: moisture left in a case corrodes steel parts and marks dials, and the damage grows the longer it stays. The leaking seal then has to be found and renewed, and the case pressure-tested, as when watch gaskets need replacing describes.
Habits that help
- Wear it under a cuff. The wrist keeps it warm, and the sleeve keeps off snow and wind.
- Keep it out of the car overnight. Taken off outdoors, it belongs in an inside pocket, not an outer one.
- Dry it, then let it warm up on its own. Wipe off snow, slush and sweat with a soft, dry cloth and leave it at room temperature, away from radiators, heater vents and hair dryers. Direct heat can take a watch far hotter than it is built for, and a hair dryer is also magnetic enough to affect a mechanical movement.
- Leave the crown and pushers alone while it is wet or cold. Seiko and Citizen both warn against working the crown of a wet watch, and a cold gasket is stiff. Set the time once the watch is warm and dry, and keep a screw-down crown screwed fully home.
- Have a winter-sports watch tested. Skiing, skating and snowshoeing bring snow, sweat and repeated swings between cold air and warm rooms, so its water resistance should be checked regularly, ideally before the season starts.
What the signs usually mean
| What you notice | What it usually means |
|---|---|
| A mechanical watch slows or stops in the cold, and stays irregular when warm | Ageing oils; a full service is due |
| A quartz seconds hand moves in two-second steps | A battery near its end; replace it soon |
| A quartz watch stops and does not restart once warm | A spent battery or a fault; do not leave a dead cell inside |
| Fog that clears within a couple of minutes of drying the glass | Condensation as the watch warms; no cause for concern |
| Mist under the crystal that stays, droplets or rust spots | Moisture in the case; have it opened and dried promptly |
When a watch does need attention, Viattori’s repair service begins with a free assessment and a written estimate, and nothing is done until the estimate is approved. Watches arrive by tracked mail from across Canada, and if opening the case shows that more is needed than the estimate foresaw, work stops and the owner is asked first.
Questions
Can cold weather damage a watch?
Rarely, if the watch is sound. Cold can make a mechanical watch run slightly off its usual rate and hold back a quartz watch’s battery, and both effects pass as it warms. The lasting risk is moisture: coming in from the cold can expose a tired seal, and mist that stays under the crystal needs a watchmaker promptly.
Is it safe to leave a watch in a cold car?
It is best avoided. Overnight, a parked car gets about as cold as the air outside, far colder than a watch on the wrist. A mechanical watch may run off its usual rate, or stop if its oils are old, and a weak quartz battery may falter. Seiko advises against leaving a mechanical watch anywhere below 5 °C.
Why is there fog inside my watch after being outside?
A cold watch brought into a warm room collects condensation, and if a seal is no longer sound, some can form inside the crystal. Citizen’s guidance is that fog which clears within a couple of minutes of drying the glass is no problem. Fog that stays, droplets or rust spots mean moisture is inside the case: stop wearing the watch, have it opened and dried promptly, and have its seals tested.
Does cold weather drain a watch battery?
Cold holds a battery back more than it drains it: a cold cell delivers its power less readily and recovers as it warms. A battery near the end of its life may trigger the low-battery signal in the cold, often a seconds hand moving in two-second steps, and should then be replaced soon, even if the watch recovers indoors.
Do mechanical watches gain or lose time in the cold?
Seiko notes that a mechanical watch tends to gain in the cold and lose in the heat, as its metal parts contract and expand. In deep cold, oils also thicken and reduce the balance’s swing, which can slow or stop a watch overdue for service. On the wrist, under a cuff, it stays near skin temperature and the effect is small.