When to go
The Cook Islands is a great destination all year round; seasonal variations are slight, with temperatures ranging between 18°C and 28°C in the winter months (May to October) and 21°C and 29°C during the summer (November to April). The Cook Islands has a pleasantly even climate year round, with no excesses of temperature or humidity, although it can rain quite often.
Thanks to its high inland mountains, Rarotonga is often quite wet, and although you'd have to be unlucky to suffer one of the rare week-long rainy spells, bring wet-weather gear with you at any time of the year just in case.
The best times of year to visit are around the months of September and October, when there's a nice trade-off between warm temperatures and reduced humidity; March and April are also good months to come, as the cyclone season has passed and the skies are likely to be clear and sunny.
The wet season is from December through to March, when around 25cm of rain can fall each month; this period is also the most likely time for cyclones, which are becoming more frequent due to warming seas across the South Pacific. On average, a mild cyclone will pass by two or three times a decade, while severe cyclones generally only hit the islands once every 20 years or so - but in 2005, an unprecedented five cyclones tore through the islands in five weeks, suggesting that cyclones may be much more difficult to predict in the future as climate change hits home.
The wet season is also the hottest and most humid time of the year - it can get quite sticky and uncomfortable, so bring along some cool, light clothes. The winter nights can sometimes be quite cool, even chilly, so if you're visiting at this time of year, a warm sweater or jacket will probably come in handy.
The only really tricky time to visit is around the Christmas and New Year period, when many Cook Islanders return home from overseas to celebrate the holiday season with their families. The flights (especially the ones from Australia and New Zealand) can get really packed around this time, and accommodation will be much harder to come by as well. The small planes to the outer islands are also generally booked up months in advance and you'll have a tough time getting a seat at this time of year.