Climate - Cook Islands

Index

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• Introduction
• North
• South - Avarua
• Cyclones

Introduction

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The climate of the Cook Islands, an archipelago in the Pacific Ocean located south of the Equator, "free association" with New Zealand, is tropical, with a rainy period from December to March and a relatively dry period from June to September, without there being a real dry season.
Rainfall is abundant throughout the country: on the northern islands, it ranges from 1,900 to 2,800 millimeters (75 to 110 inches) per year, becoming progressively more abundant from east to west, while on the southern islands, it hovers around 2,000 mm (80 in) per year.
The amount of sunshine on the Cook Islands is fairly uniform throughout the year, which means that even in the rainiest months, there is a fair amount of sunshine hours: showers are more intense and more frequent, but they do not last long and do not shield too much the sun, even in this period.

North

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The islands are divided into two groups: the northern islands, closer to the Equator (8 to 13 degrees south latitude), are warmer and have a stable temperature, around 27/28 °C (81/82 °F) as daily average throughout the year.
The main islands are Manihiki, Nassau, Penrhyn, Pukapuka, Rakahanga and Suwarrow.

Here are the average temperatures of the island of Manihiki.

As mentioned, precipitation in the northern islands decreases from west to east. The reason lies in the fact that the easternmost islands are closer to the arid zone of the Kiribati archipelago. Unlike in Kiribati, the rains on the Cook Islands are still plentiful, but during La Niña years, when the cool easterly winds that blow near the Equator from South America become more intense, the dry area becomes wider and reaches the Cook Islands, while in El Niño years, when the cool winds slow down, the sea warms up, and the frequency of cyclones increases.
Here is the average precipitation in Manihiki.

In the north, the sea temperature is high all year long, as can be seen in the following table.

South

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On the contrary, on the southern islands, from 18 to 21 degrees south latitude, there is a cooler period from June to October, when the daily average drops to around 22/23 °C (72/73 °F), while in the warmest period, from January to April, it doesn't go above 26/27 °C (79/81 °F). In July and August, at the acme of the cool period, the maximum temperatures drop to around 25 °C (77 °F) on the southernmost islands of Rarotonga and Mangaia and around 27 °C (81 °F) in Palmerston and Aitutaki.
The islands are Aitutaki, Atiu, Mangaia, Manuae, Mauke, Mitiaro, Palmerston, Rarotonga and Takutea.
From May to October, but especially from July to September, cool air can arrive from the south, which can lower the temperature to 14/15 °C (57/59 °F) at night and 23/24 °C (73/75 °F) during the day, especially in Rarotonga and Mangaia.

Avarua

Here are the average temperatures in the capital, Avarua, on the island of Rarotonga.

In Avarua, more than 200 mm (8 in) of rain fall per month from December to February, the wettest period, and about 70/100 mm (2.8/3.9 in) from June to September, the driest period. Here is the average precipitation.

On the southern islands, the sea temperature also decreases a bit in the winter months, although it remains high enough for swimming, as can be seen in the following table.

Tropical cyclones

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The Cook Islands are situated in the area of the tropical cyclones of the South Pacific, which may pass over the islands from November to April (although they are more likely from December to March). The northern islands are located right in the area where cyclones form, so they are usually still in the early stages of their life, and then evolve migrating south, although it is possible that some of them could grow rapidly, becoming intense in the same area where it has just formed.
An intense cyclone, formed a little earlier than in the normal period, was Martin, which hit the islands at the end of October 1997. Another intense cyclone was Percy, which affected the islands from late February to early March 2005.

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