Eclectic climates
As the Polynesian territory is as vast as that of Europe, the climates of the various archipelagos, all tropical, sometimes vary considerably. The Marquesas Islands lie 8 degrees south of the equator, while some of the Austral islands are above the Tropic of Capricorn. As a result, the ocean's intemperance can be more excessive in the Marquesas, causing drought and flooding. The Tuamotu atolls, for their part, are less exposed to rainfall due to their lack of mountains; freshwater, however, can become a crucial problem. Finally, the Australs enjoy a cooler, even temperate climate. It can be 10°C and sometimes hail! Rapa, the southernmost island, can even see its temperature drop to 5°C at the top of the mountains.
The sea is also warmer in the Marquesas and cooler in the Australs, where coral does not grow. With neither protective barrier nor lagoon, this gives the islands a completely different morphology.
Dry and wet season
The dry season extends from May to October (except in the Marquesas, where it rains more). This is the austral winter, the most pleasant time of the year, as a gigantic anticyclone encompasses Polynesia and hangs on. The size of the Pacific creates much larger anticyclones than those found in our latitudes. These months see temperatures of between 24 and 28°C, with the best months being July and August. But that doesn't mean there can't be a little rain. With a southeasterly wind towards the equator, the trade winds(mara'amu) are loaded with moisture. They trigger rain on the windward side, crossing the mountains and raising the temperature on the leeward side of the plain: this is the "foehn effect". With their vegetation clinging to the mountain tops, the islands are almost always covered in clouds.
The wet season extends over the rest of the year, from November to April. The southern summer, bathed in sunshine, excites the ocean's moods. Showers become more frequent, the air is saturated with humidity and the atmosphere is heavy and muggy. Thunderstorms become more violent, the wind sometimes even rips the tops off coconut palms, and the barometer can plummet further. The depression becomes weak, then medium, then strong. When it passes 117 km/h, it becomes a cyclone. Its eye appears, it howls and can spew wind and rain at over 400 km/h! Fortunately, this phenomenon remains relatively rare in Polynesia, and in reality, the rainy season simply corresponds to a period when it rains more often! The atmosphere is a little heavier, and city-dwellers more stressed. This can be an opportunity to contemplate magnificent clouds moving at full speed - so close you'd think you could touch them. They can give extremely localized showers, sometimes flooding a district of Tahiti, while the other islands are bathed in sunshine. It can even rain on the other side of the street, without a drop of rain being felt here!
Every year, a ceremony is organized to celebrate the passage between two seasons and pay homage to the Pleiades constellation: "Matari'i i ni'a" around November 20, and "Matarii i raro" around May 20.
Cyclones
While this phenomenon is fortunately rare in Polynesia, the country does occasionally find itself in the path of devastating cyclones. A cyclone is a strong tropical depression with wind speeds in excess of 117 km/h. It can extend over a diameter of more than 800 km, with winds of up to 400 km/h. At the center of a cyclone, the eye can be up to 40 km wide. Cyclones form at the same latitude as Polynesia, roughly between the Australs and the Tuamotus. Although they generally move at around 30 km/h in a southwesterly direction, it is impossible to predict their trajectory. A stormy sea forms in the vicinity of cyclones. When the tail of a cyclone passes overhead, winds blow at over 100 km/h, devastating an area even larger than the cyclone itself. If you find yourself in the eye, you're not out of the woods - far from it - but the cyclone offers an intermission: the pressure is particularly low and the winds are nil.
The Tuamotu islands, with their inhabitants living on the water's edge, are naturally the most exposed. The inhabitants of the higher islands are also exposed, but can protect themselves from rising waters by taking refuge on the mountains. In the past, the Maohis had no other way of finding out what was happening than to listen to the sea and the wind. Today, however, satellite observations enable us to anticipate and spot the presence of a cyclone, and thus to evacuate and protect ourselves. Despite all this, the means we have in place will always remain derisory in the face of the power of the elements: we are all too small in the face of Mother Nature!
Today, there is no longer much loss of life during cyclones in French Polynesia. Cyclone shelters have been built on almost all the islands; failing that, the inhabitants take refuge in the only permanent buildings in the village: the school and the church. Social housing on the islands is often made up of "fares MTR", lightweight dwellings designed to withstand 250 km/h winds. The authorities put up posters everywhere with advice on how to tie down your roof or moor your boat. Schools are generally closed on days when a major depression is forecast.
The El Niño phenomenon
El Niño, Spanish for "Baby Jesus", is a warm current that moves from west to east in the Pacific. It is so named by Peruvian fishermen, as it usually arrives at Christmas time, bringing fish to the coasts in droves. Although it has only been studied for a century, the first accounts of it date back to the 16th century, and its activity dates back over 5,000 years. This cyclical phenomenon, accompanied by cyclones, recurs every three to seven years. Much has been said about El Niño, particularly in 1997 and 1998, when it was the most powerful cyclone of the 20th century, and in 2010, when Cyclone Oli hit the Territory.
