Climate
The climate of Tonga is characterized by the contrast between a wet season (December-April) and dry season (May-November). At least some 60-70% of annual rainfall falls during the wet season. Owing to the seasonal proximity of the South Pacific Convergence Zone, the northern islands of Tonga receive more rainfall (approx. 2600 mm year-1) than the southern islands (approx. 1700 mm year-1).
Temperatures vary likewise. Mean annual temperature at Niuafo'ou is about 26 °C while on Tongatapu it is about 23 °C. This variation manifests the distinction between the tropical climate and environment of northern Tonga and the subtropical character of its southern parts.
In all parts of Tonga, evapotranspiration usually exceeds rainfall only during June and July. Severe water shortages can occur in places during these latter months, particularly in precipitation during the preceding months has been lower than usual.
The two principal causes of rainfall variation in Tonga are the occurrence of tropical cyclones, which can result in unusually wet periods, and an El Nino event, which can cause prolonged droughts. The Kingdom of Tonga thus has a tropical climate which is well suited to all tropical horticultural crops throughout the year.

Geography
Tonga is situated between; latitude 15° and 23.5° South, longitude 173° and 177° West. Tonga consists of three main groups: the Tongatapu group in the south, the Ha'apai group in the centre, and the Vava'u group to the north. Altogether there are 171 islands but only 38 are inhabited. The Tonga archipelago extends for 692 km from Niuafo'ou in the north to 'Ata island in the south.
The land area of 669 km2 is only a fraction (0.2%) of the total area of the archipelago (390,128 km2). Tongatapu is the largest southern group of islands with a land area of 257.03 km2. The Ha'apai group has a land area of 119.2 km2, while Vava'u, to the north of the Tonga ridge, is the second largest group, with 143.3 km2. Niuafo'ou and Niuatoputapu islands to the far north of the group have an area of 34.7 km2 and 18.8 km2 respectively.
Tongatapu is practically flat, rising to its highest point of 65 m at Nakolo township in the southeast. From this point the land gradually slopes down to the western-most point of 15 m at Ha'atafu township, then further slopes down to Nuku'alofa at 1 to 2 m above sea level.

Horticulture
Mainly vegetable production and fruit growing.

Distribution of Horticulture
Vegetable production and common fruit trees are found throughout Tonga. Main production is found on the main island Tongatapu. The second largest island, Vava'u, is the major kava and vanilla growing area of Tonga.

Research Thrusts
The major research thrusts is the Ministry of Agriculture and Forests. Small groups of growers carry out their own research but most often base on their own observation but not scientifically design.

Nature of Institutes
Research-Extension Division is to contribute to the Ministry of Agriculture and Forest's strategic goals through adaptive research, technology transfer and participatory systems, and to communicate with farmers about appropriate technical, market advice and farm management information.

Organisations / Institutes:
Ministry of Agriculture and Forestry

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