Below are my notes for visiting the Cook Islands. These travel tips, such as the best time to visit the Cook Islands are obtained from a variety of sources including some of the following: my first hand observations, personal conversations, magazines, newspapers, websites, books and so forth. Whenever I hear something that interests me about the Cook Islands, I jot it down here. Hope this comes in handy.
The Cook Islands are farther east than New Zealand, in the same rough vicinity as the Islands of French Polynesia. They are 15 inhabited islands.
Best Time to Visit the Cook Islands
Short Answer: Mid-May and October.
Longer Answer: The best time to visit the Cook Islands is generally between mid-May and October. From November to April, the rains increase and the humidity spikes making the already heightened temperatures feel that much hotter. August and September are good months if you want to see whales while visiting the Cook Islands.
If you do visit in the May to October timeframe, note that water temperatures will be warmest in May, cooling progressively through August and then starting to increase again. The warmest water temperatures in the Cook Islands is typically in January and February (just like the air temperatures).
Miscellaneous Travel Tips for the Cook Islands
Most people are interested in the southern Cook Islands, namely choosing between Aitutaki and Rarotonga. Aitutaki is the slower, more peaceful, chilling island with great snorkeling/diving. Rarotonga is (relatively) more action/activities.