Ask two people on the same island what the weather is doing and you can get opposite answers. One is under grey drizzle on a mountain road; the other is on a beach twenty minutes away, reaching for more sunscreen. Island weather is rarely one forecast. It is a series of local arguments between wind, sea and land, and once you know who is doing the arguing, you can read a forecast properly and plan a day that actually works.

The Wind Decides Almost Everything

In the tropics and subtropics, the prevailing winds blow from the east: north-easterly north of the equator, south-easterly south of it. These are the trade winds, and their steadiness is the single biggest reason islands have a wet side and a dry side, and why one coast can feel fresh and breezy while another sits still and humid.

They tend to be most consistent during the drier months and slacken or shift when the wet season arrives, which is why a January visit and a July visit to the same island can feel like two different places. Under the subtropical high-pressure belts, warm moist air near the surface often sits beneath a lid of drier, more stable air. That lid keeps most showers shallow and brief. Break through it — usually by climbing a mountain — and you get proper rain.

Windward and Leeward: Two Islands in One

Push moist sea air against a hillside and it rises, cools, and condenses into cloud and rain. That is the windward side, and it is generally greener, wetter and cloudier. On the far side, the air descends, warms and dries out, creating a rain shadow. This is why the contrast can be so stark: Hilo and Kona on Hawai'i, the green north and arid south of Tenerife, the lush interior of St Lucia against its drier western bays.

The sea behaves the same way. Windward coasts pick up the swell and the chop; leeward coasts are calmer, which usually makes them better for swimming and snorkelling, though less reliable for surfing. Two practical consequences:

• Choose your base by coast, not by island. If you want dry, sunny evenings, stay leeward. If you want waterfalls and cloud forest, stay windward and accept the odd soaking.
• Plan boat trips on the sheltered side. A crossing that is flat on one coast can be genuinely rough on the other, and small operators will often cancel accordingly.

Why Afternoons Cloud Over

There is a daily rhythm to island weather that is surprisingly reliable. In the morning, land heats faster than the sea. Air rises over the island and cooler air flows in from the water — the sea breeze. By early afternoon that converging air has often built into cumulus clouds over the interior, and those clouds can drop a short, heavy shower. As the land cools in the evening, the breeze reverses and the cloud usually fades.

So if you have one big outdoor plan — a summit hike, a long boat crossing, a cycle around the coast — do it early. Late afternoon cloud sitting on a mountain is not always rain, either. Cloud forest is exactly what it sounds like: a hillside permanently wrapped in moisture that never quite falls. Take a light waterproof and stop worrying about it.

Storm Seasons, Basin by Basin

Tropical cyclones are the same phenomenon with different names: hurricanes in the Atlantic and eastern Pacific, typhoons in the north-west Pacific, cyclones in the Indian and south Pacific oceans. They need warm ocean water, generally above about 26°C, which is why the seasons follow the warmest seas rather than the calendar.

• North Atlantic — Caribbean, Bahamas, Bermuda, US East Coast: 1 June to 30 November, with the busiest stretch usually from mid-August to late October.
• Eastern Pacific — Mexico's Pacific coast, and occasionally Hawai'i: from mid-May to the end of November.
• North-west Pacific — Philippines, Taiwan, southern Japan: storms are possible year-round, with the peak broadly July to October.
• North Indian Ocean — Bay of Bengal and Arabian Sea: two shorter windows either side of the monsoon, roughly April to June and October to December.
• Southern Hemisphere — South Pacific, Australia, Indian Ocean: roughly November to April.

Two things worth remembering. Storms can occasionally form outside these windows, so the dates are a guide rather than a guarantee. And a season is not a washout: most days in a storm season are sunny, with systems passing through every week or two. What you will notice first is often the swell — long lines of waves rolling in from a storm hundreds of miles away, arriving days before any wind does.

How to Read an Island Forecast

Island forecasts are coarse. A single figure for "the island" usually comes from one weather station, often at an airport on the coast, and it cannot possibly describe a place with several climate zones. A few habits will get you much further:

1. Look at wind direction and speed first. It tells you which coast will be wet and which will be calm, and it matters more than the temperature number.
2. Use the map view, not the town list. Zoom in on your specific bay and check the forecast for the nearest headland.
3. Read rain probability as "somewhere on the island". A 60% chance may mean one afternoon shower over the hills that never reaches you.
4. Watch a radar or satellite loop. Showers move with the wind, so you can usually tell whether something is twenty minutes away or will miss you entirely.
5. Check swell and tide for anything coastal. Tide times change daily, and a path that is easy at low water can be impassable at high.
6. Adjust for altitude. Temperature falls by roughly 6°C for every 1,000 metres you climb, so a 28°C coast can mean a cool, windy 16°C at the summit.

Humidity matters too. A hot day with heavy air feels far more draining than the same temperature in a dry breeze, so build in a slow middle of the day rather than fighting it. Near the equator the sun is strong even under thin cloud, so shade and cover are worth more than optimism.

Planning Around the Weather

Book the weather-dependent things — boat trips, dives, summit walks — early in your stay, so you have days left to reschedule if the wind picks up. Keep mornings for the plans that matter and leave afternoons flexible. Pack a light waterproof and a dry bag regardless of the season; they weigh almost nothing and save whole days.

Do not cancel a plan because the forecast says scattered showers. Do take official warnings seriously, follow local advice during a named storm, and check that your travel insurance covers weather-related disruption before you go. Above all, ask locally: the person running the guesthouse has watched this bay for years and will know far better than any app whether the cloud will burn off by eleven.

Photo: Peggy Anke / Pexels