Index


Introduction



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



The islands are divided into two groups: the northern islands, closer to the Equator, are warmer and have a stable temperature, around 27/28 °C (81/82 °F) as daily average throughout the year.
Here are the average temperatures of the northern island of Manihiki.
Manihiki - Average temperatures
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Min (°C)252425252524242424242424
Max (°C)303131313130303030313130
Min (°F)777577777775757575757575
Max (°F)868888888886868686888886

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.
Manihiki - Average precipitation
MonthJanFebMarAprMayJunJulAugSepOctNovDecYear
Prec.(mm)3302702251851451451151501401752452952420
Prec.(in)1310.68.97.35.75.74.55.95.56.99.611.695.3
Days21171413111191010121518161

In the north, the sea temperature is high all year long, as can be seen in the following table.
Manihiki - Sea temperature
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Temp (°C)292929292929282828292929
Temp (°F)848484848484828282848484

South



On the contrary, on the southern islands, there is a cooler period from June to October, when the daily average drops to around 21/22 °C (70/72 °F), while in the warmest period, from January to April, it doesn't go above 25/26 °C (77/79 °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, although the night temperatures remain in both cases around 20 °C (68 °F). However, from June to September, sometimes, the night temperature can drop to around 15 °C (59 °F) in Rarotonga and Mangaia.

Avarua

Here are the average temperatures in the capital, Avarua, on the southern island of Rarotonga.
Avarua - Average temperatures
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Min (°C)232323222120191919202122
Max (°C)282929282726252526262728
Min (°F)737373727068666666687072
Max (°F)828484828179777779798182

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.
Avarua - Average precipitation
MonthJanFebMarAprMayJunJulAugSepOctNovDecYear
Prec.(mm)2302702501701201007080801401802201910
Prec.(in)9.110.69.86.74.73.92.83.13.15.57.18.775.2
Days151615131210888121414145

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.
Avarua - Sea temperature
MonthJanFebMarAprMayJunJulAugSepOctNovDec
Temp (°C)272728272625242424242526
Temp (°F)818182817977757575757779

Cook Islands

Tropical cyclones



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.

Best Time



The best time to visit the Cook Islands runs from mid-May to mid-October on the northern islands, where it's hot and muggy, but tempered by the trade winds; downpours can sometimes be intense, but they do not last long, so the sun will shine again soon.
As regards to the southern islands, the best time is more or less the same, from mid-May to mid-October, but you will find lower temperatures, less abundant rains (though still possible), and the trade winds, which may sometimes be a bit cool for those who are sensitive to cold. It will therefore be useful to bring a sweater or a sweatshirt for the evening.

What to pack



In winter (June to August), bring light clothes for the day, a scarf for the breeze, a sweatshirt for the evening, possibly a light jacket for the southern islands, and a light raincoat or umbrella.
In summer (December to February), bring light clothes of natural fibers, a sun hat, a scarf for the breeze, a light sweatshirt for the evening, and a light raincoat or umbrella.

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