Reading the Weather Before a Long Countryside Walk

Start with the Sky, Not the Forecast

Before you pull on your boots, step outside and look up. The sky over Britain is rarely blank, and a quick glance can tell you a great deal about the next few hours. The trick is to read the shapes and the direction they are moving, not just whether it looks grey.

• Cumulus humilis — small, flat-bottomed clouds spaced like sheep on a hillside. These are the fair-weather clouds of a pleasant walking day.
• Cumulus congestus — the same clouds growing taller, with cauliflower tops and darkening bases. By early afternoon they can produce showers, especially over high ground.
• Cirrus — high, wispy streaks, often called mare's tails. Arriving from the west in a blue sky, they usually mean a warm front is on its way, with rain within a day or so.
• Lenticular — smooth, lens-shaped clouds stacked over a summit. They are beautiful, but they signal strong winds and turbulence on the ridge. Save the high tops for another day.
• Cumulonimbus anvil — a flat top spreading like a blacksmith's anvil. Expect thunder, lightning, hail and sudden squalls. Get low, avoid exposed ground and metal fences, and head for shelter.

Wind Direction and the Shifting Veer

The UK sits under a prevailing south-westerly, so most of our weather arrives from that quarter. Turn to face the wind and note its direction on your cheek or the back of your neck. A wind that backs — shifting anticlockwise, say from south-west to south to south-east — often heralds deterioration. A wind that veers — south-west to west to north-west — frequently brings clearing skies and cooler, showery air. Neither rule is perfect, but together they help.

On the coast, watch for the sea breeze. A warm morning can be almost still, then by early afternoon an onshore breeze picks up and pushes a line of cloud inland. On the east coast this can bring haar, a cold, damp fog that rolls in quickly and cuts visibility on cliff paths. Inland, wind funnels through cols, valleys and gaps in the hills, arriving stronger than the general forecast suggests. Smoke from a chimney, the tops of trees and the movement of grass all show you the truth at ground level. If low cloud moves one way and high cloud another, a front is close.

What the Pressure Is Really Telling You

A barometer at home is a wonderful thing, but you can read pressure without one. Falling pressure usually means unsettled weather on the way. A slow fall over a day or two suggests rain within thirty-six hours. A rapid fall of one or two hectopascals per hour is a serious warning of a deepening storm, and a day for a low-level walk rather than a ridge.

Rising pressure generally brings clearing skies, though often with a cold, showery westerly and excellent visibility. If you have no instrument, look for natural signs. Pine cones close their scales as humidity rises. Damp air carries sound well, so a train, a waterfall or traffic that suddenly seems louder than usual can be a hint of rain approaching. Valley mist on a still autumn evening is another sign of moisture.

Ground Signs and Wildlife Clues

Look down as well as up. Heavy dew on the grass on a spring morning usually follows a clear night and often precedes a fine day. A morning with no dew at all suggests cloud has trapped the night's warmth, and rain may not be far away. Valley mist that burns off by mid-morning is a classic sign of a settled day ahead; mist that thickens and lifts into low cloud is the opposite.

Wildlife is worth watching. Swifts and swallows feeding high in a blue sky indicate high pressure and rising insects. When they hunt low, skimming hedges and water, insects are being pushed down by damp, heavy air — a good clue that rain is coming. Sheep turning their backs to the wind, or huddling in a field corner, tell you it is strengthening. Midges and horseflies are often worse in the still, humid hours before a front arrives.

A Five-Minute Check Before You Set Off

Stand at the door and run through a simple routine. Look at the horizon in every direction, but pay special attention to the west and south-west, where most of our weather comes from. Face the wind and note its direction, then compare it with the forecast you checked earlier. Look at the cloud types and how fast they are moving. If you have a barometer, note the trend, not just the reading.

Pack for the day the weather might become, not the weather you have now. A waterproof, an extra warm layer, a map and compass, a torch, food and water are sensible even on a bright morning. Tell someone your route and your expected return time.

Finally, know your turning-back triggers. An anvil cloud, thunder, a rapid pressure fall, wind backing and strengthening, or visibility dropping below your comfort level are all reasons to shorten the walk and head for lower ground. Reading the weather is not about predicting it perfectly. It is about noticing enough to make good decisions, and enjoying the countryside safely whatever the sky decides to do.