I HAVE A SIMPLE STRATEGY for planning my diving year. UK diving from April through to August. In September and October, I switch my attention to the Med, then from November through to March I do hot and tropical.
 That's not to say that you can't get good diving in these places at other times of the year, or even that my strategy results in the best time to be there. I like to make the most of the best conditions for UK diving, and everything else gets fitted around it.
 It doesn't always work out that way. Sometimes I manage unusually good UK diving in midwinter, when the odds are stacked against me. Sometimes it makes sense to break into my UK season for an overseas trip, not necessarily for the peak of the good diving weather, but to avoid the worst times of year, or see a particular critter.
 Many warmwater locations have diving year-round - it's just that at some times of year, a trip is at greater risk of foul weather than at others.
 

The Caribbean, Gulf of Mexico and Western Atlantic
Every year we hear of another big hurricane devastating an island or two in the Caribbean before venturing ashore somewhere in Central America or the southern United States, wrecking the coast and causing damage inland until it fizzles out to become a mere storm.
 Last year's hurricanes were unusually violent, and diving destinations such as the Cayman Islands and Grenada took a terrible battering.
 The key to it all is energy. There is a stupendous amount of energy in a hurricane. Take all the world's nuclear weapons and set them off in one big bang and it would still provide only enough energy to keep a hurricane going for a day or so.
 The energy is drawn from the sea. A warm sea results in a rising air current as surface water evaporates. With a large enough body of water, the critical temperature for a hurricane to form is 26.5°C.
 A hurricane also requires wind conditions that allow the rising air to stay together rather than being dispersed. When the rising air currents stay together, air to replace that mass is drawn in from the sides, which in turn gathers heat and moisture from the sea and rises in the middle, forcing the rising air higher and higher into the atmosphere.
 The final thing needed to get a hurricane moving is coriolis, the pseudo- force arising from a combination of the Earth's rotation and the conservation of angular momentum. The result is that the rising hot moist air starts to spin and form an anti-clockwise spiral, sucking more energy from the surface of the sea and feeding the process as the wind gets faster and faster.
 When wind speed exceeds 74mph, the tropical storm becomes a hurricane, force 12 on the Beaufort scale.
 The risk is greatest when the sea is warmest. The hurricane season runs from June to November, with more than a third of all hurricanes occurring in September, when the sea temperature can get as high as 28°C.
 Hurricanes usually move west and then north, so islands such as Bonaire off the Venezuelan coast are away from the main track. Over land, a hurricane soon loses energy. It is rare that a hurricane reaches as far as 100 miles inland.
 East Pacific
 The word hurricane comes from Hunraken, the Mayan god of winds, so the same term is used to describe a force 12 storm off the western coast of Central America. Once again, the peak season is when the sea is at its warmest in September.
???? Hurricanes form in the warm water off Central America and move west into the Pacific, so the good news for this coastline is that hurricanes move out to sea and rarely make landfall.
???? A hurricane needs warm water to feed and survive. With cold currents running south down the North American coast and north along the South American coast, any hurricane that strays north or south and out of the general westward drift will be over cooler water and lose energy before it makes landfall.
 The last hurricane to hit Southern California was in 1935.
 Further into the Pacific Ocean, Hawaiian waters are too cold for new hurricanes to form, though occasionally one strays westward across the Hawaiian Islands.
 South America
 South of the Caribbean and Central America, even though water can be warm enough, coriolis decreases towards the Equator and there just isn't enough spin for hurricanes to form.
 Further south, the sea is colder and there just isn't enough heat. Hurricanes are not a consideration when planning trips to destinations like the Galapagos, which is guarded by cold currents.
 What you have to bear in mind when planning a trip south of the Equator is that the seasons are conveniently reversed. Midwinter is 21 June and midsummer is 21 December, nicely complementing the UK diving season.
???? I never have a problem remembering this, though I have to force myself to think twice when navigating by the sun, as it is due north at midday.

Central and North-west Pacific
West of the international dateline you don't get 'hurricanes' - the terminology changes to 'typhoon', derived from the Chinese daaih-fung, meaning 'great wind'. North of the Equator, the sea is at its warmest - and hence typhoons are most likely - between August and December.
 The most vulnerable islands are Guam and the northern Marianas, which lie right in the middle of the storm track. Further south Palau; Yap; the Federated States of Micronesia, which include Chuuk; and the Marshall Islands, which include Bikini Atoll, see fewer typhoons, with the southernmost islands being too close to the Equator for typhoons to be a problem.
???? North-east trade winds provide a refreshing breeze through most of the year, but tend to die off during late summer and autumn, when the climate becomes more humid and sticky.

South-west Pacific, Australia
In the South-west Pacific and Australia, the name changes again. Where the sea is warm enough, hurricanes or typhoons are now referred to as 'tropical cyclones'. The only physical difference is that they now spin clockwise, as coriolis goes the other way south of the Equator.
 Coupled with the switch in seasons compared to the northern hemisphere, the tropical cyclone season runs from December through to May, with the highest risk in March, when the sea is warmest.
???? As in central America, the western coast of Australia is at a much lower risk, as the path of tropical cyclones is generally from east to west, so tropical cyclones forming north of Australia tend to move out to sea.
 Further south in Australia and in New Zealand the sea is cooler and normal weather patterns prevail, though you still have to remember that the seasons are reversed south or the Equator.
 Cyclone comes from the Greek kykloma, which means 'coiled serpent'. On the UK shipping forecast the term 'cyclonic' is used to refer to winds moving in a clockwise pattern about an area of high pressure. Having said that, north of the Equator in the Indian Ocean the terminology can be really confusing.

Indian Ocean, South-east Asia
; In the Arabian Sea and Bay of Bengal, where the storm patterns are anti-clockwise (anti-cyclonic), the term 'tropical cyclone' is still used. Tropical cyclones occur in the Bay of Bengal year-round, but are rarest from January to March.
 It's not just wind, but rain and storm surge, that has caused some of the biggest natural disasters in history. In the middle of an intense low pressure the sea level rises. Wind then pushes the sea higher still, particularly in areas where the land has a funnelling effect.
 Storm surge can raise the sea level as high as 12m. Land surrounding the Bay of Bengal is typically low and close to sea level, so a tropical cyclone can cause widespread flooding hundreds of miles inland.
???? While unfortunate for those who live there, the Bay of Bengal is not a major diving destination, though the north-east coast of Sri Lanka occasionally suffers. On the other side of India, in the Arabian Sea, tropical cyclones form in May, June, October, November and December.
???? South of India, the Maldives straddle the Equator, so while the water is nice and warm, there isn't enough coriolis to get a tropical cyclone up to speed. The word you hear with regard to the weather across the Indian Ocean and South-east Asia is 'monsoon'.
 Monsoon derives from mausim, the Arabic for season,. It is not a word for bad weather in itself - or for torrential rain, as is often thought - it's just a word used to describe the changing of the seasons.
 From May to October, during the summer in Asia, the land warms up, air above it rises and air is drawn in across the ocean to create a wind pattern that is predominantly from the south-west.
 It's a bit like the onshore afternoon breeze we get in summer, but on a global scale.
 The south-west monsoon brings the wet season and most of the rain to the Maldives, with days of torrential rain, particularly in August and September, though there can be extensive dry spells during the wet season. In winter, the continental land cools and the wind patterns reverse to give the north-east monsoon and the dry season.
 In Sri Lanka, at the entrance to the Bay of Bengal, most of the diving is on the west coast and the diving season coincides with the north-east monsoon.
 In Thailand, the diving season switches coast with the monsoons, the prime Andaman Sea (west coast) season being during the north-east monsoon, and diving in the Gulf of Thailand being in season in the south-west monsoon.
 The same applies to some extent in peninsular Malaysia, though further south towards Tioman and Singapore the climate becomes more equatorial and diving is an all-year activity, as it is throughout most of Indonesia.
 Just as you are starting to get the hang of weather patterns in this part of the world, everything changes and it all goes the other way.
???? The wet season in Malaysia and most of Indonesia comes with the north-east monsoon, between October and April, though which months are traditionally wettest varies from island to island.
???? The Philippines, on the border between the Pacific and South-east Asia, are exposed to typhoons in the north-east, but this is well away from the main diving locations. Most places popular for diving in the Philippines are sheltered and good for diving throughout the year, with the wet season coming with the south-west monsoon.
 While monsoon times are pretty much fixed with the calendar, the direction varies towards the edges of the region. The Seychelles are too close to the Equator for tropical cyclones, but have a wet season with a north-west monsoon from November to April. They arewindiest near the start of the wet season.
 Further south, Mauritius and Reunion islands both get a distinctly stormy season and the occasional tropical cyclone, with the highest risk being between January and April, as these islands are south of the Equator.

East and South Africa
Bordering on the warm water of the Indian Ocean, the climate of the East African coast is influenced by both the continental land mass and the warm water of the ocean. The coastlines of Kenya and Tanzania tend to be stormy and wet during April and May.
???? South of the Equator, in Mozambique, the hot rainy season is from October to March, though Madagascar provides some shadow from the rain, particularly towards the south.
???? The tropical influence decreases further south into South Africa, with more conventional seasons which are, of course, the opposite way round to those of the northern hemisphere.

Red Sea, Persian Gulf
Having come to equate hurricanes and their ilk with warm water that is not on the Equator, an obvious question is: 'Why don't they occur in the Red Sea or Persian Gulf?' The water is certainly warm enough in the summer and autumn.
 The answer is compound. These partly enclosed bodies of water are just too narrow. Any storm that began to grow big enough would overlap the edges and lose energy to friction with the land well before it could become a tropical cyclone. Secondly, wind patterns don't allow any rising mass of warm moist air to remain stable, another of the conditions for a tropical cyclone to form.
???? Compared with hurricanes, typhoons, tropical cyclones and monsoons, weather in the Red Sea is a bit of a non-event. It's a desert. There is no rainy season. It's milder in winter and hotter in summer. Occasional rain is a relief. Occasional sandstorms are choking.
 Traditional methods of navigation rely on spotting breaking waves in order to locate reefs and steer round them. In perfect calm conditions, boat captains may actually decide to go slower, as the reefs are harder to spot!
???? In the Persian Gulf, diving is towards the eastern end, where summer is both hot and humid, with air temperatures regularly above 40?C. From May through to October it can be just too hot to go diving. It's most comfortable to be there during the winter and spring.

Mediterranean
Climate in the Mediterranean can generally be summarised as European, but further south. Seasons are pretty much what we are used to, but warmer and in many places drier.
 Dive centres in some popular destinations may operate year-round, but bear in mind that on some days the sea gets too rough to dive, particularly in the winter.
 Dive centres in the less-popular destinations may close for the winter, or operate only at weekends for local divers.
 In the north-western Mediterranean, the Mistral is a cold, dry northerly wind caused by air cooling and falling from the Alps and Pyrenees, particularly in winter. It doesn't stop you diving, but you may want warmer clothes.
 Mistral is often followed by exceptionally good underwater visibility, as algae is killed off by the cold conditions.
 The Bora is a similar cold wind that comes from the north across the former Yugoslavian countries and along the Adriatic. Some time in autumn, the air temperature in Croatia suddenly drops.
 The Sirocco is a warm dusty wind from the Sahara to the south. Crossing the Mediterranean, it gathers moisture and brings warm but dirty rain.

East Atlantic
The climate in the Canaries is moderated by the Canaries current from the north, taking the edge off the heat in the summer and giving mild winters. Diving is reliably year-round.
 The main wind patterns are from the north and north-east, making the north ends of the islands more exposed and the sea conditions less dependable for diving. Most dive centres are based to the sheltered southern sides of the islands.
 As in the Mediterranean, an easterly Sirocco wind from the Sahara can bring warm and misty air.


After the storm - a dive centre was here


Considering the force of the storm, this yacht is remarkably intact


Storm waves destroy a seafront


The sea soon settles and divers are in the water







So why dive in the wet or stormy season?
While sun worshippers are driven predominantly by the surface weather, divers may be prepared to risk rain or storms for better diving. Ocean currents change with the monsoon. In some places the good visibility comes with the stormy or wet season. In some places there are many more fish at that time, or the best chance of big animal encounters. With the dry-land tourists staying at home, you may also get a bargain price.