Seasons and climate
 Visit
Tahiti and her islands, get sun throughout the year !
French Polynesia is a tropical destination with lots
of sun and just enough rain for its luxuriant
vegetation and its colorful flowers.
It receives in average 2,500 to 2,900 of sunshine per year. (ie : 8
hours of sun per day). Temperatures range between 24°C and 30°C all
year through and lagoon water temperature varies between 23°C and 26°C. |
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Thus, the climate of Polynesia -defined as marine tropical- is
hot (average air temperature is 26.5°C) and humid (hygrometry :
75%) but tempered by the ocean. Thus, Polynesia is submitted to
northeast and southeast trade winds converging to the equatorial
zone which create 2 distinguished seasons : the dry season
and the humid season.
- The dry season -also called Austral winter- taking place
between April and October brings an expected coolness, July and
August being the coolest months of the year due to southeast trade
winds called maraamu. As a consequence a cotton sweater
will often be enjoyable in the evening (or early in the morning).
- The humid season -also called Rainy season- starts in
November and ends in March. It brings mugginess, humidity as well
as heavier and more frequent rains than in the dry season. During
that season, tropical storms may occur. Winds can reach speeds
of over 220 km/h and can eventually evolve to a cyclone, an extremely
rare event though. French Polynesia was touched lastly by cyclones
at the beginning of the 90’s after having been hit 6 consecutives
times in 1982-1983 (this had not happen since 1906 !). These cyclonic
events are due to a well know phenomenon called “El Nino” (see
below for more details).
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Yearly average data in Tahiti
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Average temperatures |
Average rainfalls |
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Located in an inter-tropical zone, French Polynesia presents a
certain climatic unity. However, as French Polynesia is spread
on a surface as large as Europe, the climate will change slighly
from one archipelago to the other. In the Austral archipelago
(south) that includes some islands located south of the Capricorn
tropic, the climate is more tempered and low temperatures can reach
10°C during the dry season. In the Marquesas islands (north), the
dry season occurs between August and December. Due to a lack of
relief, the Tuamotu archipelago (east) receives less rainfalls than
the others as the clouds don’t encounter mountains to stop them.
Finally, high islands (such as Tahiti, Moorea or Bora Bora) feature
micro-climates related to their altitudes and exposition.
Eastern coasts are more exposed to trade winds and consequently
receive more rainfalls than the western coasts that are more sheltered.
El Nino
This phenomenon has been studied by meteorologists for many years
and it is well-known for its unpleasant consequences and more specifically
for its role in the development of cyclones and hurricanes.
Actually, El Nino is a periodical marine draft whose
activity is not considered abnormal since it has been active for
the past 5,000 years. What is abnormal is its high frequency in
the latest years. It usually appears around Christmas time
(that is why it has been named El Nino – the Child). It occurred
in 1972/73, 1975/76, 1982/83, 1986/87, 1991/92 and 1997/98 (the
strongest of the century). Using the effects of trade winds, El
Nino is responsible for bringing down along the coasts – from
western to eastern Pacific - hot waters of equatorial regions.
Normally, trade winds make high pressure subtropical air to converge
towards equatorial low pressure regions, drawing along with them
hot ocean waters from East to West. But when those trade
winds weaken, they reverse (change round) and consequently they
draw with them those same hot water from West to East. This constitutes
el phenomenon called “El Nino”.
In eastern Pacific, water temperatures are usually below 25°C.
Those hot water currents make the average ocean water temperatures
to increase by 3 to 4°C. This increase generates a succession
of climatic anomalies, characterized in Polynesia by trade winds
inversion and sometimes the birth of a cyclone when the
ocean temperatures is over 28°C.
El Nino is only a small part of a more global climatic
fluctuation system called E.N.S.O. ( El Nino Southern Oscillation).
The research program TOGA (measurements of atmospheric air pressures
taken in the regions of Darwin - North of Australia - and Tahiti)
associated with TOPEX-POSEIDON and JASON 1 programs (*) made it
possible to understand and detect this phenomenon. Pressure differences
between Tahiti and Darwin constitute a good indicator of El Nino
phenomenon.
(*) JASON 1 : satellite program measuring the sea-level altitude
at 500,000 different points on the earth.
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