The northern fells are generous on a clear day. You set off for a high tarn, rucksack packed with a towel and a flask, the sun on your back and a swim in mind. But the British weather rarely signs a contract. Within an hour, cloud can swallow the ridge, the wind can swing round, and rain can arrive like a curtain. Knowing what to do when the weather turns is not about being cautious to the point of never going out. It is about coming home with a story rather than a rescue.
Weather on the fells changes faster than any forecast can capture. A morning of blue sky can turn by lunchtime. The first signs are often subtle: a lowering cloud base, a sudden drop in temperature, a backing wind, or the first spots of rain on your map case. If you are heading for a tarn, watch how the water surface changes from glassy to choppy. That is your cue to think about a different plan. Trust your senses as much as your phone. If the cloud is already down on the summit you hoped to reach, it will not lift just because you have driven three hours to get there. Ask yourself: can I navigate safely if visibility drops to twenty metres? If the answer is no, adjust your route now.
The hardest decision on the fells is often the wisest. Turn back early, before the weather fully commits. Set a turn-around time before you set off, and stick to it. If you are twenty minutes from the summit but the cloud is thickening and the wind is strengthening, turn around. The summit or tarn will still be there next week. Pushing on to a distant objective when the weather is deteriorating is how small problems become serious ones. Remember that the descent can be harder than the ascent: wet rock, slippery grass, and tired legs. A known route back is worth more than a view you cannot see. If you are walking in a group, make the decision together and be clear about it. No one should feel pressured to continue.
On open fells, shelter is rarely a bothy or a convenient tree. You need to use the landscape. Look for the lee side of a crag, a large boulder, a hollow, a dry stone wall, or a gully. Avoid ridge lines, summits, and the shore of an exposed tarn, where wind and rain hit hardest. If you are already at a tarn when the weather breaks, get out of the water immediately. A tarn that was calm ten minutes ago can turn into a churning grey pool. Once out, dry off quickly, put on dry layers, and eat something. Shelter is not just about stopping the wind; it is about stopping heat loss. A group of you can huddle together for warmth. If you have an emergency shelter or a bothy bag, use it, but do not rely on it as a first resort. Natural features are often closer and more reliable.
When visibility drops, stop. Get your map and compass out before you lose sight of features. Take a bearing to a known point — a wall corner, a stream junction, a path — and then follow it. Do not press on to a distant summit or tarn. Instead, follow a bearing back the way you came, or to a safe handrail that leads you down. Count your paces. If you have a GPS device, use it as a backup, not a replacement. The skill of following a bearing is what gets you home when the cloud is down and your phone is wet. If you were heading to a tarn, reverse the bearing you used to get there. If you cannot remember it, take a new one from your current position to a known feature. A known bearing is safer than a hopeful guess. Practise this on clear days so it becomes second nature when you need it.
Wild swimming in upland tarns is one of the great joys of northern Britain. But it demands respect, especially when the weather turns. If you are already in the water when the cloud comes down, get out. Cold rain and wind on wet skin accelerates heat loss. Dry off, dress in warm layers, and shelter. Do not attempt a long swim in a remote tarn if the cloud is down and the wind is up. Save it for a settled day. Even in summer, upland tarns can be bitterly cold, and cold water shock is a real risk. If you are with others, keep an eye on each other for signs of hypothermia: shivering, slurred speech, clumsiness. Get someone warm and sheltered, and be prepared to descend. The tarn will still be there next week, and it will still be cold and clear.
Once the squall passes, take stock. Are you warm? Is everyone okay? Do you still have a safe route? Sometimes the best decision is to descend the way you came, even if the summit is tantalisingly close. Other times, you can continue with a revised plan, using natural shelter and bearings. The fells will always be there. The tarn will still be waiting. What matters is that you come back. Fell walking and wild swimming are about freedom, but they are also about judgement. Turning back early is not failure; it is the mark of an experienced hillgoer. So pack your map, your compass, and your warm layers. Enjoy the tarns. But when the weather turns, listen to the fells and act early.
Northern Tarn shares practical, down-to-earth guidance on upland tarns, fell walking and wild swimming in northern britain for readers across the UK.
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