Climate French Polynesia
The climate in Polynesia is, so to speak, heavenly! The warm, tropical atmosphere and airy trade winds are what every visitor hopes to find in Tahiti: ideal weather. Tempered by the immense ocean, the heat is rare and the balance is maintained between 24°C and 27°C throughout the year: not too hot, not too cold! Take advantage of this to swim in the lagoon, which is always 29°C. In the evening, a simple T-shirt will suffice, or even a little wool in the Austral Islands: there is rarely more than a 5°C difference between day and night. By ensuring constant evaporation, the ocean maintains a humidity level of around 60-80%, which means that rainfall is twice as high as in Paris during the year. Rainfall is usually intense and frequently spaced out, but it has nothing in common with the heavy and suffocating equatorial climate of the Amazon or Asia, alternating showers and bright sunshine.
Eclectic climates
As the Polynesian territory is as large as that of Europe, the climates of the different archipelagos, all tropical, sometimes present important differences. The Marquesas Islands are located 8 degrees south of the equator, while some islands in the Austral Islands lie beyond the Tropic of Capricorn. As a result, the ocean weather can be more excessive in the Marquesas Islands, causing drought and flooding. The Tuamotu atolls, on the other hand, are less exposed to rainfall due to their lack of mountains; however, freshwater can become a crucial problem. The Austral Islands have 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 on the mountain tops.
The sea is also warmer in the Marquesas and cooler in the Austral, where corals do not grow. Since they form neither a protective barrier nor a lagoon, this gives the islands a completely different morphology.Dry and wet season
The dry season runs from May to October (except in the Marquesas, where it rains more). This is the austral winter, which is the most pleasant period because a gigantic anticyclone encompasses Polynesia and remains stuck there. The size of the Pacific generates anticyclones much larger than those found in our latitudes. These months rotate between 24 and 28 °C, the best months being July and August. But this does not prevent some light rain. Under a south-easterly wind towards the equator, the trade winds (mara'amu) are laden with humidity. They trigger rains on the windward side, cross the mountains and increase the temperature on the leeward side of the plains: this is the "foehn effect". With their vegetation clinging to the tops of the mountains, the islands are almost always topped with a cap of clouds.
The wet season extends over the rest of the year, from November to April. The southern summer, bathed in sunshine, excites the moods of the ocean. Showers are more frequent, the air is saturated with humidity and the atmosphere is heavy and moist. Thunderstorms become more violent, the wind sometimes even tears off the tops of the coconut trees, and the barometer can still fall. The depression takes the name of weak tropical, then medium, then strong. When it exceeds 117 km/h, it becomes a cyclone. Its eye appears, it screams and can spit wind and rain at more than 400 km/h! Fortunately, this phenomenon remains relatively rare in Polynesia, and in reality, the rainy season is simply a period when it rains more often! The atmosphere is a little heavier, and city dwellers are more stressed. This can be the occasion to contemplate magnificent clouds moving at full speed - so close to us that one would think one could touch them. They can give extremely localized showers, sometimes flooding a district of Tahiti, while the other islands are bathed in sunshine. Sometimes it even rains on the other side of the street, without you even feeling a drop of rain here!
Every year, a ceremony is organized to celebrate the passage between two seasons and pay tribute to the Pleiades constellation: "Matari'i ni'a" around November 20, and "Matarii i raro" around May 20.
Cyclones
Although the phenomenon is fortunately rare in Polynesia, the country sometimes finds itself on the path of devastating cyclones. A cyclone is a strong tropical depression with wind speeds exceeding 117 km/h. It can extend over more than 800 km in diameter, with winds of up to 400 km/h. At the centre of a cyclone, the eye can be up to 40 km wide. Cyclones form at the same latitude as Polynesia, roughly between the Austral Islands and the Tuamotus. Although they generally move at about 30 km/h towards the southwest, it is impossible to predict their trajectory. In the vicinity of the cyclones, a stormy sea forms. As the tail of the cyclone passes through, winds blow at more than 100 km/h, devastating an area even larger than the size of the cyclone itself. If you find yourself in the eye, you're not out of the woods - far from it - but the cyclone gives you an intermission: the pressure is particularly low and the winds are zero.
The Tuamotu, with its inhabitants living on the water's edge, are of course the most exposed. The inhabitants of the high islands are also exposed, but they can protect themselves from the rising waters by taking refuge on the mountain. If the Maohis once had no other way to find out about the Tuamotu than to listen to the sea and the wind, satellite observations now allow us to anticipate and detect the presence of a cyclone, and thus to evacuate and protect ourselves. In spite of everything, the means put in place will always remain derisory in the face of the power of the elements: here we are, tiny little ones in the face of Mother Nature!
Today, there are not many human losses during cyclones in French Polynesia. Anti-cyclone shelters have been built on almost all the islands; otherwise, the inhabitants take refuge in the only permanent buildings in the village: the school and the church. Social housing in the islands is often made of "MTR lars", light dwellings designed to withstand winds of 250 km/h. The authorities put up posters everywhere with advice on how to attach your roof or moor your boat. Generally, on days when a major depression is forecast, schools are closed.The El Niño phenomenon
El Niño, or "the Infant Jesus" in Spanish, is a warm current that moves from the west to the east of the Pacific. It is so named by the fishermen of Peru, because it usually arrives at Christmas time and brings fish in masses to the coast. Although it has only been studied for a century, the first accounts mentioning it date back to the 16th century and its activity dates back more than 5,000 years. This cyclical phenomenon, accompanied by cyclones, occurs every three to seven years. Much has been said about El Niño, especially in 1997 and 1998, as it was the most powerful cyclone of the twentieth century, and in 2010 with Cyclone Oli, which hit the Territory.
