The most important piece of weather information to remember about Rarotonga is that it is in the Southern Hemisphere. Winter is from June to August, and summer is November through March. However, even if you are from the Northern Hemisphere and forget this crucial distinction, your trip won’t be ruined - the Cook Islands are actually warm year round. Rarotonga’s winter average is 25 degrees Celsius, and the summer average is about 28 degrees Celsius. It does rain more in the summer, so you will need a small umbrella, or light rain jacket, for brief, warm downpours.  Take a torch at night to avoid the puddles along the road berms due to the sudden heavy downpours!

Hurricane season overlaps with summer, but it is not really a “season” as you’d typically think of the word, because storms usually come only once every other year. Hurricane winds blow in from the north, and by the time they’ve reached Rarotonga, they are usually not strong enough to cause severe damage to the interior of the island.

Here are some web sites you can use to check on the weather in the Cook Islands:

The Fiji Met Service   Click on regional country forcasts and then Cook Islands.

This one is specific to Aitutaki and is especially good for wind surfers  windfinder  There is no comparable one for Rarotonga.

This site is probably the best one for checking for hurricanes/cyclones: U.S. Navy Hurricane Center

Lastly here is a site that shows satellite images of the South Pacific. The small dot just East of 160W and just North of 20S is Aitutaki. The small dot just South of that just below 20S is Rarotonga

Be aware that weather can change very quickly in the tropics. It can be rainy at 8 o'clock in the morning and by 10 it can be full sunshine.