The weather doesn't wait for your jacket

British hills have a particular talent for changing character in the time it takes to eat a sandwich. You set off under pale blue sky on a still morning in the Lakes, and by the time you reach the col the cloud has dropped, the wind has swung round and a fine, insistent drizzle is finding every gap in your collar. It is rarely dramatic. It is just quietly, persistently cold — and that is exactly what catches people out.

The mistake most walkers make is not choosing bad clothing. It is waiting too long to put it on. Once you are cold and wet, you are managing a problem rather than preventing one. The trick is to treat your layers as something you adjust constantly, not something you decide once at the car park.

Layering: three jobs, three layers

Think of your system as three separate jobs rather than three garments.

• Next to skin: something that moves sweat away from you. A synthetic or merino base layer works well; cotton does not. Cotton soaks, holds water against your skin and pulls heat out of you fast. Leave the everyday t-shirt at home.
• Mid layer: this is your insulation, and it should be easy to remove without taking your shell off. A fleece or light synthetic jacket fits the bill. On a breezy ridge you may want it; on a steep climb you almost certainly will not.
• Outer shell: windproof and waterproof. This is the layer that decides whether a mediocre day becomes a miserable one.

The point of layering is that you can add and remove small amounts of warmth without stopping for long. Ten seconds of faffing beats ten minutes of shivering.

Sweat is the silent chill

Here is the thing nobody tells you on the way up: getting too hot is the beginning of getting too cold. If you climb a long, steep ascent in full kit you will sweat heavily, your base layer will soak, and the moment you stop — at a summit, a stile, a photo — the wind will chill that damp fabric against your skin. That is when people start to shiver.

The fix is unglamorous but effective. Start slightly cool. Open your vents and pit zips on the climb. Take your hat off before you think you need to. Slow down a fraction on the steepest sections so you are breathing hard but not overheating. Eat and drink little and often, because a tired body regulates temperature poorly.

A good rule: if you are sweating hard, you are wearing too much for the effort you are making. Strip a layer before you start the ascent, not after.

The windproof shell moment

Wind is the great amplifier. A temperature of 5°C in still air is a pleasant hill day; the same 5°C with a 40 mph wind on an exposed ridge feels closer to freezing, and that windchill strips warmth from any exposed skin and any damp clothing.

So watch for the moment. If you feel the first prickle of cool air through your mid layer, if the sweat on your back suddenly feels cold, if you are turning your face away from the wind — stop and put your shell on. Not at the next cairn, not at the summit. Now. Add your hat and gloves at the same time. It takes two minutes and saves an hour of discomfort.

On high ridges the wind can arrive with the cloud, almost without warning. Having your shell at the top of your pack, rather than buried underneath your lunch, is worth more than any gadget you could carry.

Small extremities, big consequences

Cold hands and feet ruin days out of all proportion to their size. Blood is pulled towards your core when you chill, so your fingers and toes are the first to suffer and the last to recover.

• Gloves: carry a pair of thin liner gloves and a warmer waterproof pair. Liners let you fiddle with map, zip and snack without exposing bare skin.
• Hat and buff: a huge amount of heat leaves through your head and neck. A buff doubles as a scarf, a hat and a way to keep spindrift off your face.
• Spare dry gloves and a spare hat in a dry bag. This is the single best morale insurance you can pack.
• Food you can eat with gloves on. If it needs two hands and a knife, it will not get eaten on a windy summit.

Ridge days: pace, fuel and turning back

Ridge days ask more of you than valley walks, because you are exposed for longer and there is rarely a convenient sheltered spot. Plan the day around the forecast, but assume it will be worse than predicted. Build in an escape route — a descent off the ridge, a lower path, a shorter circuit — and decide now, while you are warm and comfortable, what conditions would make you use it.

Keep moving steadily rather than in bursts. On a long ridge, small regular pauses for food and drink beat one long shivering stop. If someone in your group is getting quiet, clumsy or slow, treat it as a cold warning rather than a personality trait. Get them into shelter, into dry layers, into warm food and drink, and reassess honestly.

British hill weather rewards humility and preparation, not heroics. Layer smartly, shed heat before you sweat, add your shell before you chill — and you will be able to enjoy the ridge for what it is, even when the rain and wind arrive.