Rarotonga and Aitutaki, which are about as far south of the equator as the Hawaiian Islands are north of it, enjoy a tropical climate. Even during the summer months of January and February, the high temperatures on Rarotonga average a comfortable 84°F (29°C), although there can be hot, humid, and sticky summer days. The climes are much more pleasant during the winter, from June to August, when the average high drops to 77°F (25°C), and the ends of Antarctic cold fronts can bring a few downright chilly nights. It's a good idea to bring a light sweater or jacket for evening wear during the winter months.
December through April is both the cyclone (hurricane) and rainy season. There always is a chance that a cyclone will hit during these months (three struck almost back-to-back early in 2005), but most of the rain comes in short, heavy cloudbursts that are followed by sunshine. Rain clouds usually hang around Rarotonga's mountain peaks, even during the dry season (June to Aug).
In short, there is no bad time weather-wise to visit the Cook Islands, although the shoulder months of April, May, September, and October usually provide the best combination of sunshine and warmth.
Holidays & Events
Legal holidays are New Year's Day, Anzac (Memorial) Day (Apr 25), Good Friday, Easter Monday, the Queen's Birthday (first Mon in June), Gospel Days (last Mon in July and Oct), Constitution Day (Aug 4), National Gospel Day (Oct 26), Aitutaki Gospel Day (Oct 27, Aitutaki only), Christmas Day, and Boxing Day (Dec 26). Government offices and many businesses are closed on Monday if a holiday falls on a weekend.
The busiest season is from late June through August, when New Zealanders and Australians escape their own winters. Make hotel reservations early for these months. Many Cook Islanders live in New Zealand and come home for Christmas; you can easily get a room, but airline seats are hard to come by during that holiday season.
The three major national festivals are the Dancer of the Year Contest, in mid-April; the Cook Islands National Self Governing Commemoration, in early August; and Tiare Week, the first week in December.
Swinging Hips -- I never visit the Cook Islands without watching the hips swing at a traditional dance show. Take my word for it: Had the crew of HMS Bounty seen the dancing on Rarotonga instead of Tahiti, even Captain Bligh might have mutinied! The best times to see the best dancing come during the Dancer of the Year contest in mid-April and during Cook Islands National Self Governing Commemoration in early August.
Note: This information was accurate when it was published, but can change without notice. Please be sure to confirm all rates and details directly with the companies in question before planning your trip.