Start with a forecast, then read the sky yourself

A forecast tells you what the models expect. The sky tells you what is happening above your head right now, and in the uplands those two things can part company quickly. Before you leave the car park, check a reliable forecast for the exact area you plan to walk — not the nearest town, which may sit in a sheltered valley with a very different story. Then spend two minutes looking up, feeling the wind on your face and noting the temperature. That habit turns a list of numbers into a picture you can update all day.

Cloud shapes worth learning

You do not need to become a meteorologist. Half a dozen cloud types cover most of what you will meet on British hills.

• Cumulus — the fair-weather puffs, flat-based with plenty of blue between them. Small and well separated, and you have time on your side.
• Cumulus congestus — the same clouds growing taller and darker through the morning. A build-up like this is your cue to think about descending earlier than planned.
• Cumulonimbus — the full anvil with a flattened top. Expect hail, lightning and a violent, icy gust beneath it.
• Lenticular — smooth, lens-shaped stacks that sit still while everything else moves. A classic sign of very strong winds at ridge level.
• Cirrus and altostratus — high wisps thickening into a milky sheet. Rain usually follows within a few hours.
• Nimbostratus — featureless grey that erases the tops. Not dramatic, just wet, cold and disorientating.

Watch the height of the cloud base as much as the shape. Cloud sitting low on a plateau means you lose the view that keeps you oriented.

Wind direction tells you where the weather is coming from

Wind is the most reliable of the signs and the easiest to measure — face it and note the direction. In the UK, an easterly in winter often brings dry, sharp cold; a south-westerly is the classic mild, wet, windy direction off the Atlantic. The interesting part is change.

A wind that backs — shifting anticlockwise, say from south-west to south to south-east — often warns that a low is approaching and conditions are about to worsen. A wind that veers — clockwise, from south through south-west to west — usually means the worst has passed and clearer air is arriving behind it. It also helps to remember that in the Northern Hemisphere, standing with your back to the wind, lower pressure lies to your left.

On the hill, wind is rarely steady. It accelerates over ridges, funnels through gaps and can gust hard on lee slopes, which feel deceptively calm one minute and hostile the next. Note the point at which wind starts to affect your walking — that is when to adjust your plan.

Pressure, and the feel of a day turning

Pressure changes matter more than pressure values. A steady reading, high or low, means settled weather for now. A falling barometer points to an approaching front, often with wind rising and cloud thickening at the same time; the faster it drops, the more energetic the system tends to be. A rising barometer brings showers that clear quickly, good visibility and a cold, clean feel to the air.

Your own senses are a serviceable instrument. If the air suddenly feels close and heavy, or the wind drops to nothing on an exposed summit and the silence feels odd, that calm is often the quiet ahead of a squall. If the cloud base lifts off a summit you could not see an hour ago, the day is improving.

Ground-level signs on heathland and moor

Upland heath and blanket bog give you clues of their own — and they deserve your care too.

• Sheep and cattle turning their backs to the wind and drifting downhill are heading away from the worst of it, not just seeking comfort.
• Birds feeding low, then a sudden burst of activity, often signal a change on the way.
• Valley mist forming late on a still afternoon usually means a cold, clear night ahead — but it can thicken into fog rapidly around dusk.
• Wet ground after long rain is fragile ground. Peat hags and heather clumps take years to recover from heavy trampling, so stick to established paths and stone flags rather than cutting across eroded bog.

Heather turns the hill purple in late summer, while the burnt patches you see in spring are part of rotational management that keeps the habitat open and varied. Expect seasonal restrictions on some moorland access when the fire risk is high, and respect any signage.

Prepare for the shift, not just the forecast

Upland weather changes faster than a valley forecast suggests, so build in margin.

• Carry waterproofs and a spare insulating layer even on a warm morning.
• Pack map, compass and headtorch; do not rely on a phone battery that shrinks in the cold.
• Take food and a hot drink, and know your escape routes before you need them.
• Tell someone your route and expected return time.
• Set a turnaround time or decision point — a summit, a wall, a stream crossing — and hold to it even if the weather seems fine.

The hills are generous with beauty and unforgiving of complacency. Read the sky, listen to the wind, watch the barometer, and the day will be both safer and far more interesting.