The number to dress from
Use the feels-like figure, not the air temperature. You are moving through air, so wind matters, and feels-like is the number that accounts for it — see what "feels like" means.
Then apply the rule every experienced cold-weather runner uses: dress for 10 to 20 °F (5 to 10 °C) warmer than it says. You will generate a great deal of heat within the first mile, and clothing that felt right at the door will be too much by the end of the street.
The practical test: standing outside before you start, you should feel slightly underdressed. If you are comfortable standing still, you are overdressed for running.
One thing the forecast does not include: your own pace adds to the effective wind. Running at 10 km/h into a 15 km/h headwind gives you 25 km/h of air movement over your face, so the outbound leg into the wind is colder than the number suggests — and the return leg, with wet clothing and a tailwind, is where people get cold.
What to wear, by feels-like
| Feels-like | Layers | Extremities |
|---|---|---|
| 10 to 15 °C (50–60 °F) | Shorts, short sleeves | Nothing |
| 4 to 10 °C (40–50 °F) | Shorts or tights, long sleeves | Light gloves if windy |
| 0 to 4 °C (32–40 °F) | Tights, long sleeve, light windproof | Gloves, headband |
| −7 to 0 °C (20–32 °F) | Tights, base layer, windproof jacket | Gloves, hat, buff |
| −12 to −7 °C (10–20 °F) | Thermal tights, two upper layers, windproof | Insulated gloves, hat, buff over the face |
| −18 to −12 °C (0–10 °F) | As above plus wind briefs, thicker socks | Mittens, full face covered |
| Below −18 °C (0 °F) | Consider running indoors instead | |
Three principles behind the table:
Windproof matters more than thick. A thin windproof shell over a base layer beats a heavy fleece with nothing over it, because moving air is what strips heat off you.
Cover the extremities first. Your torso is generating heat; your fingers and ears are not. A hat and gloves buy more comfort per gram than any jacket.
Nothing cotton. Cotton holds sweat against the skin and stops insulating the moment it is wet, which turns the second half of the run into the cold half.
Where the real limits are
The thresholds worth knowing, and they are about exposed skin rather than about toughness:
- Down to −10 °C (14 °F): comfortable for most runners with the layers above.
- −10 to −18 °C (14 to 0 °F): manageable, but cover all skin and shorten the run. Check the wind chill rather than the air temperature.
- Wind chill below −27 °C (−18 °F): frostbite on exposed skin within about 30 minutes. Any skin left uncovered is on a clock.
- Wind chill below −32 °C (−26 °F): treadmill weather. The margin for a zip failing or a glove getting wet has gone.
Those wind chill figures come from the published frostbite exposure bands, which are in wind chill explained, and the calculator will work them out for a given temperature and wind speed.
Ice is the bigger risk than cold
At the temperatures most people run in, the injury risk is a fall rather than the cold itself.
The dangerous conditions are the marginal ones — around freezing, after a thaw and refreeze, on a clear morning following a wet evening. Black ice on a shaded path or a bridge deck is invisible and gives no warning.
Practical responses: shorten your stride and land flatter-footed, avoid painted lines and metal covers, treat bridges and underpasses as icy by default because they freeze first and thaw last, and accept a slower pace. If it is genuinely icy, trail shoes or spikes change the calculation entirely.
Run out into the wind and back with it. Into the wind you are dry and generating heat; on the way home you are damp, and a headwind on wet clothing is where cold runs turn unpleasant. It costs nothing to plan and it is the single most useful habit in this list.
Afterwards
The coldest part of a winter run is usually the ten minutes after it.
Get out of wet layers immediately rather than standing about — evaporative cooling from damp clothing in cold air drops your temperature fast once you have stopped generating heat. Have dry clothes ready before you leave, not waiting at the bottom of a drawer.
And drink. Thirst is a much weaker signal in the cold, and you lose water through breathing dry air as well as through sweat, so it is entirely possible to finish a long cold run properly dehydrated without ever having felt thirsty.