Start with the sky, not the tackle box

Most anglers plan a session around where they fancy fishing, then check the weather to see whether they need a coat. It pays to work the other way round. Fish are cold-blooded, and almost everything they do — where they hold, how deep they sit, whether they feed at all — is driven by water temperature, light levels and changes in air pressure. Twenty minutes with a forecast the night before will tell you more about your chances than a new rig ever will.

None of this is about waiting for perfect conditions. It is about choosing the swim, the species and the tactics that suit the day you have actually been given. A blustery south-westerly on a Midlands lake asks for a different approach to a flat calm, frosty morning on a chalk stream.

Wind: direction first, strength second

In the UK our prevailing wind is south-westerly, and that is usually good news. It arrives off the Atlantic, so it is mild and often damp — a south-westerly in January can lift water temperatures enough to switch fish on. A northerly or easterly is the opposite: cold, clear, and frequently hard work, particularly from late autumn through to March.

On lakes and reservoirs, fish the windward shore when you can. Wind pushes surface plankton and drifting invertebrates downwind, and the resulting colour and chop gives fish confidence. The foam line and scum edge at the far end of a big pit is rarely an accident. That said, be sensible — a force five or six is miserable and potentially dangerous, and casting into a gale is futile. In those conditions, drop back to the near bank and fish with the wind off your shoulder.

On rivers and streams, a wind pushing against the flow is a gift. The ripple it creates breaks up the surface and gives fish cover to feed in shallow, otherwise-exposed runs. Dead-calm, gin-clear stretches on a small river in summer will often fish far worse than a ruffled one.

Cloud cover and light levels

Light is the single biggest factor for wary fish in clear water. On bright, high-sun days, roach, chub, carp and even perch pull into weed, shadow, undercut banks and deeper water. You can still catch, but you need to fish early, fish late, or fish tight to shaded features — often with lighter line and a smaller bait.

Overcast skies change everything. Diffuse light means fish spread out and feed confidently for longer. Grey, mild days are classic tench, bream and roach weather, and they are the days when a river will produce chub right through the afternoon rather than just at dawn.

Do be careful to distinguish grey and mild from grey and bitter. Thick low cloud with a biting easterly is a different proposition entirely, and it is rarely productive.

Air pressure: read the trend, not the number

Average sea-level pressure is roughly 1013 millibars. What matters is not so much the reading as the direction it is moving and how fast.

• High and settled — above about 1020mb. Often bright and clear, and in winter that usually means frost and cold water. Fish can be slow and reluctant.
• Falling pressure — the classic feeding window. The twelve to twenty-four hours before a front arrives often produce the best sport of the week, especially on rivers.
• Low and unstable — below about 1005mb. Wind, rain and changeable conditions. Fish frequently feed hard, but presentation becomes difficult.
• A sharp rise after a deep low is the one to watch for. It often switches fish off for a day or two as they adjust.

A steady spell of two or three days at a similar pressure is almost always better than a day right on a swing.

Rain, cold fronts and water temperature

Rain is not automatically bad. In summer, a warm shower aerates the water and adds a little colour, and fish often respond well. On rivers, a gentle lift in level and a touch of colour is one of the best barbel and chub triggers there is — the falling, clearing water after a spate is prime time on many venues.

The cold front is the one to respect. When a band of rain is followed by cold air, water temperatures can drop several degrees in a single night, and fish will often shut down completely for twenty-four to forty-eight hours. Look for the second or third settled day afterwards. Warm, mild rain in winter riding in on a south-westerly is a very different beast from cold rain behind a northerly, and the fishing reflects it.

Water temperature matters far more than air temperature. A mild 12°C afternoon means little if the lake has been chilled by three frosty nights.

A simple pre-trip routine

Before you load the car, run through this and you will make better decisions on the bank:

• Check the pressure trend across the last forty-eight hours, not just today's figure.
• Note wind direction and strength, and pick your bank at home rather than in the car park.
• Look at the cloud forecast hour by hour to decide whether to fish dawn, dusk or all day.
• Check overnight minimum temperatures — frost means cold water and often a slow start.
• Look at rainfall over the last day or two on the specific river catchment you are fishing.
• Always have a plan B swim, ideally on the opposite bank, so the wind can be used either way.

Weather is not an excuse for staying indoors. It is information, and reading it properly is one of the few things in angling that costs nothing and pays almost every time.