Running in cold or hot weather: what to wear, hydration and warning signs

TUREFF• •0

Running through the seasons is part of the fun, and with a little preparation you can run safely in most weather. Heat and cold both put extra strain on the body, though, and both can become dangerous. This guide covers how to dress, how to adjust your training, and the warning signs to know. It is general information; anyone with a heart condition or other medical condition should ask a doctor about exercising in extreme temperatures.

Cold weather: dress in layers

Base layer: a close-fitting synthetic or wool top that moves sweat away from your skin. Avoid cotton, which stays wet and cold.
Mid layer: a light long-sleeved top or fleece for colder days.
Outer layer: a windproof, ideally water-resistant jacket.
Extremities: a hat or headband, gloves and warm socks. Much of the discomfort of cold running is in the hands and ears.
Dress so you feel slightly cold for the first few minutes. Once you warm up, you will be comfortable; overdressing leads to heavy sweating, and wet clothes chill you later.

Cold weather: adjust your run

Warm up indoors for a few minutes before stepping out.
Run into the wind at the start, so you have it behind you when you are sweaty on the way back.
Watch for ice. Shorten your stride on slippery ground, and run on a treadmill or indoors when it is truly icy.
Wear reflective or lit gear on dark winter mornings and evenings.
Change out of wet clothes straight after the run.
You still sweat in the cold, and thirst can be blunted, so keep drinking.

Warning signs of cold injury

Frostnip and frostbite: numbness, then pale, waxy or hard skin, usually on fingers, toes, ears, nose and cheeks. Get indoors and warm the area gently; seek medical help if the skin stays numb, hard or discoloured.
Hypothermia: early signs include strong shivering, cold hands and feet, and fumbling. As it progresses, shivering may stop, and confusion, slurred speech, clumsiness and drowsiness set in. This is a medical emergency: call for help, get the person somewhere warm and dry, and remove wet clothing.

Hot weather: acclimatise gradually

Your body adapts to heat over about one to two weeks of regular exercise in it, sweating earlier and keeping your heart rate lower. The adaptation fades if you stop. For the first hot weeks of the year, or after travelling somewhere hot, run shorter and slower and build up.

Hot weather: adjust your run

Run early or late, avoiding the hottest part of the day.
Choose shaded routes, and routes with water.
Slow down. The same pace costs far more in heat and humidity. Go by effort, not by your watch.
Wear light-coloured, loose, breathable clothing, a cap or visor, sunglasses and sunscreen.
Humidity matters as much as temperature: sweat cannot evaporate to cool you when the air is already damp.

Hydration and electrolytes

Start runs well hydrated, and drink during runs of more than about an hour, or less in strong heat.
On long or very sweaty runs, a drink with electrolytes, or salty food, replaces what you lose in sweat.
Drink to thirst rather than forcing down large volumes. Too much plain water over many hours can lower blood sodium to dangerous levels.
Weighing yourself before and after a run shows roughly how much fluid you lost; pale yellow urine is a reasonable everyday sign you are drinking enough.

Warning signs of heat illness

Heat exhaustion: heavy sweating, headache, dizziness, nausea, cramps, weakness, and feeling very hot. Stop, get into shade, drink, and cool down. If it does not improve quickly, get medical help.
Heat stroke: a medical emergency. Signs include confusion, odd behaviour, slurred speech, collapse or seizures, with a very high body temperature. Skin may be hot and dry, but people with exertional heat stroke can still be sweating. Call emergency services, and cool the person as fast as possible while you wait: move them to shade, remove extra clothing, and use cold water and ice, especially on the neck, armpits and groin.

In any extreme weather

Tell someone your route, or run with others, in extreme weather.
Carry a phone.
Have an indoor alternative ready, and do not feel you have to run in every condition. Missing one run is better than missing weeks.

What is the hottest or coldest weather you have run in, and what did you learn? Share your tips or questions in the comments.