Tongan Island has a tropical climate throughout the year and it’s reflects its location within the trade wind zone of the South Pacific region.
Tonga’s wet season, which lasts from November to April, and the dry season is from May to October. The highest Temperatures were recorded 35.0 °C on the 11th February 1979 in Vava’u while 33.1 °C was recorded in Nuku’alofa on February 2002. February is the hottest month of the year. The wettest month is March and the driest month varies between June and July but the coolest month is July or August event though some extreme low temperatures often occur in September.
In fact, warm clothes are occasionally required from June to August so plan your Tonga travel accordingly. However, the lowest temperature on record is 8.7°C on the September 8, 1994 in Fua'amotu.
From early July to late October it's currently known as the Whale Seasons. This is when the whales from the Antarctic travel all the way to the Island of Tonga and end up at the beautiful Island Group of Vava'u.
Humpback Whales migrate each year to the Kingdom of Tonga to mate and give birth and stay at the area approximately 15 weeks before returning back to the Antarctic.
Tropical cyclones are confined to the wet season which is also called the Cyclone Season. February is the month with the highest frequency of cyclone occurrence on Tonga. The average number of tropical cyclone to affect Tonga in a season is between 1 and 2. In the event of an El Nino, the frequency of cyclone occurrence increases.
The north winds in February and March are hot and moisture laden. The southeast winds blow from May to November, while the easterlies blow over the island the rest of the year. Bad weather is heralded by the west and northwest winds.
While moving from Tongatapu in the south to the more northern islands near the equator, the temperature rises from 23 °C to 27 °C (74 °F to 80 °F). The annual rainfall increases too from 1,700 to 2,500 millimetres.