Tonga consists of 171 islands spread over an area of 748 km², of which 36 islands are inhabited. The islands are in four main groups: Tongatapu, Vava’u, Ha’apai, Niuatoputapu and Niuafo’ou. The capital Nuku’alofa is located on the main island of Tongatapu and has a population of approximately 34,000 people.

Tonga is highly vulnerable to a range of natural disasters and, as its population is predominantly in low-lying coastal areas and spread over small isolated islands, response efforts are often difficult.

In 2015, a drought warning was declared. The National Emergency Management Office is urging people to get ready for a looming water crisis. Tonga has had extremely dry weather for nearly a year and three months of low rainfall is expected as El Nino strengthens its grip on the region. For more information on El Niño in the Pacific visit: The Pacific El Niño Hub 

Cyclones are the most frequently occurring disaster, with an average of one per year. In February 2012, Cyclone Jasmine brought heavy rains and flooding to Tonga, which had been impacted by Cyclone Cyril a week prior. The worst cyclone in the history of Tonga took place in 1982, killing six people and impacting 146,512.

In January 2014, Tropical Cyclone Ian tracked between Fiji and Tonga for several days before intensifying to a Category 5 system with winds over 200 kilometres per hour. In the early hours of 11 January, the cyclone swept east of the Vava’u group before passing directly over Ha'apai in the afternoon. A state of emergency was declared for Vava’u and Ha’apai the same day. There was one fatality, 14 injuries and extensive damage to houses, infrastructure and agriculture. A total of 534 houses were destroyed and 398 were damaged. Around 2,335 people sought shelter in 51 formal and informal shelters. On 21 January, the Government accepted international assistance from the Pacific Humanitarian Team who supported national clusters for the first time. OCHA ROP supported response planning and information management, while the PHT deployed expertise in WASH, Health, Protection, Livelihoods, Food Security and Shelter. The three-month response plan totalled US$15.1 million.

In addition to cyclones, natural hazards in Tonga include earthquakes and volcanic activity. Tonga lies very close to the convergence of the Australian and Pacific tectonic plate, one of the most seismically active areas in the Pacific. The most recent major earthquake to impact the population occurred in May 2006, although no deaths or injuries were recorded. There is a volcano on the island of Niuafo’ou and the last major eruption in 1946 caused the island to be completely evacuated.

Due to its seismic activity, Tonga is also vulnerable to tsunamis. The last significant tsunami hit Niuatoputapu in September 2009. Nine people were killed when six to 17 metre-high waves came inland 600 m and destroyed many villages.

WHO, UNDP and UN Women have a presence in Tonga.