Weather locations in Cook Island

The Cook Islands are a self-governing group of fifteen islands spread across more than two million square kilometres of the south-central Pacific, between roughly 8°S and 25°S, with Rarotonga and Aitutaki at the heart of the chain. They sit squarely in the trade-wind belt of the tropics, so there is no real cold season; the weather is warm, humid and breezy all year. Rarotonga and Aitutaki are volcanic and hilly, rising to about 650 metres, while the northern islands are low coral atolls.

Main climate types

All of the islands fall into the tropical rainforest group of the Köppen classification, with rain in every month rather than a true dry season, though the amount varies a good deal between islands and years. The southern, volcanic group is wetter and hillier, while the northern atolls are flatter and drier. One or two months around mid-year are usually the driest, when the trade winds freshen.

Temperatures

Conditions are remarkably steady. On Rarotonga the mean sits at about 24 °C or 25 °C in every month, and the difference between the warmest and coldest month is only two or three degrees. Daytime highs are usually in the low to mid 30s °C, but the sea breeze keeps them from feeling oppressive, and evenings rarely drop below about 20 °C.

Rainfall

Rain falls mostly in short, heavy bursts rather than all day. Rarotonga receives roughly 2,000 mm a year and Aitutaki somewhat less, perhaps 1,500 mm to 1,900 mm. Wettest months are usually January to March, when the trades relax, and the driest period runs from May to October. The higher, south-eastern slopes of Rarotonga are much wetter than the sheltered north-west side.

When to go

Because the temperature barely changes, the season depends on rain and wind. The trade-wind months from about May to October are dry, clear and breezy, the best time for sailing and diving. The wetter, warmer months from November to April bring more rain and a higher chance of tropical cyclones.