Rarotonga & the Cook Islands Weather in September

What is the Weather Like in Rarotonga and the Cook Islands in September?

Experience the best of every season during September in Rarotonga and the Cook Islands. Warm tropical temperatures and low humidity make September a comfortable month to lap up the sun in the Cook Islands without getting too hot. What’s more, September lies between the tourist high season and low season, making it a great time of the year to experience the ideals of the Cook Islands’ “winter sun” without having to pay the full price for resorts and flights. It’s the perfect time to come to the Cook Islands to relax, as well as seek adventure with the seasonal whale watching and clear waters for snorkelling and scuba diving.

Although you don’t really need to worry about the Rarotonga and Cook Islands weather in September, here’s some more information about the temperatures, rainfall, daylight hours and more.

Before we jump into this weather guide for September, be sure to bookmark Rarotonga & the Cook Islands Weather, Seasons & Climate and The Best Time to Visit the Cook Islands for more advice.

5 Tips for Visiting the Cook Islands in September

The nights feel considerably cooler than the day, so you’ll be glad to pack a light jacket
The sea conditions are ideal in September for scuba diving, snorkelling, kitesurfing and even spotting humpback whales, so add those to the bucket list
September marks the end of the busy season in the Cook Islands. Still, a bit of planning is recommended; we recommend booking your trip at least two weeks in advance
While September is still in the dry season, there are often a few rainy days
Be sure to apply high-factor reef-safe sunscreen often.

Rarotonga & the Cook Islands Weather in September

Typical Temperatures in September

Temperatures are steadily back on the rise, as September is the season between the Cook Islands’ winter and summer. September allows you to experience the best of both worlds with warm temperatures expected in a tropical climate but less humidity.

Expect the maximum average temperatures to reach 26°C / 79°F and the minimum average temperatures to go down to 19°C / 66°F usually at night.

Temperatures Across the Cook Islands

Rarotonga – The average maximum temperature is 26°C / 79°F and the minimum average temperature is 19°C / 66°F
Aitutaki – The average maximum temperature is 28°C / 82°F and the minimum average temperature is 21°C / 70°F
Mangaia – The average maximum temperature is 26°C / 79°F and the minimum average temperature is 19°C / 66°F
Mitiaro – The average maximum temperature is 27°C / 81°F and the minimum average temperature is 21°C / 70°F
Manihiki (North) – The average maximum temperature is 30°C / 86°F and the minimum average temperature is 24°C / 75°F
Penrhyn (North) – The average maximum temperature is 31°C / 88°F and the minimum average temperature is 24°C / 75°F.

Sea Temperature in September

The average sea temperature in September in Rarotonga and the Cook Islands is 24°C / 75°F, some of the coldest sea temperatures of the year.

Hours of Sun in September

Considering it’s the “dead of winter” in September in the Cook Islands, days are still long with around 12 hours of daylight each day. Visitors will also experience some sun, with an average of 3 bright sunshine hours each day – not particularly sunny but comfortable.

UV Levels During September

September is the winter month in the Cook Islands with the highest UV levels, so wearing sunscreen is essential. The UV level in September is typically 10 UV index around midday. For sunscreen advice, check out The Best Sunscreens for the Cook Islands + Sun Protection Tips.

Sunrise and Sunset During September

September has daylight hours lasting about 12 hours a day in the Cook Islands.

Sunrise: 6.48 am at the beginning of September and 6.21 am at the end of September
Sunset: 6.30 pm at the beginning of September and 6.37 pm at the end of September.

Learn about the local time zone in What is the Rarotonga & the Cook Islands Time Zone?

Rainfall in September

Short bursts of rain are what to expect in terms of rainfall in September. With only an average of 5 days of rain in the month, you don’t have to worry about spending too long getting soaked by the skies. Like always, the Northern Cook Islands experiences more rain than the Southern Cook Islands.

The Cook Islands receives an average of 132 mm / 5.2″ of rainfall in the month of September, with around 5 days out of September experiencing rain.

Average Rainfall Across the Cook Islands

Rarotonga – The average rainfall in September is 132 mm / 5.2″
Aitutaki – The average rainfall in September is 90 mm / 3.5″
Mangaia – The average rainfall in September is 102 mm / 4″
Mitiaro – The average rainfall in September is 78 mm / 3.1″
Manihiki (North) – The average rainfall in September is 141 mm / 5.6″
Penrhyn (North) – The average rainfall in September is 135 mm / 5.3″.

Tropical Storms in September

The South Pacific cyclone season starts in November and ends in April. As such, September is one of the best months to avoid tropical cyclones in the Cook Islands with a very low risk of tropical storms developing.

Other months that have a low risk of tropical storms in the Cook Islands include June, July and August. Find out more about tropical storms in our guide, Cyclone Safety in the Cook Islands.

Best Places to Visit in the Cook Islands in September

Any part of the Cook Islands is stunning to visit during this warm, dry and pretty quiet time of the year. While we list all of the Cook Islands in What are the 15 Islands in the Cook Islands? for inspiration, a few places worth checking out in the Cook Islands during September include:

Rarotonga – Rarotonga is a hotspot for island holidays in the Cook Islands and for good reason. The largest island in the cooks has a high-quality tourism infrastructure, including resorts and tours. It’s also the arrival island for international flights, making for an easy fly-and-flop getaway. Find out more about what Rarotonga is all about in the 50 Best Things to Do on Rarotonga.

Aitutaki – For similar reasons as visiting Rarotonga, Aitutaki is worth visiting in September for its developed tourism scene. However, Aitutaki is still much less visited than Rarotonga, effortlessly offering a tranquil South Seas getaway. Learn more about what to do in Aitutaki in the 20 Best Things to Do on Aitutaki.

Mangaia – The southernmost island of the Cook Islands is fast becoming a popular island to visit thanks to its amazing deep caves, coral cliffs and historic maraes, burial chambres and churches. The island is much less developed than Rarotonga and Aitutaki, making for a true Pacific experience. See what Mangaia is all about in the 15 Best Things to Do in Mangaia.

Again, any of the islands are decent to visit during September, so we recommend researching more on the subject using A Guide to the Best Islands of the Cook Islands.

September Packing List for Rarotonga and the Cook Islands

Be prepared for the Cook Islands in September by packing these few seasonal essentials:

Light clothing layers for the day (cotton or linen preferably so it is super light)
Light long-sleeved tops/jacket (to take the edge off those slightly cooler nights or to keep warm after boat trips)
Light pants/trousers/skirt (to cover the knees when appropriate – church service or to protect from mosquitoes when hiking, for example)
Sunhat
Sunglasses
Swimwear
Closed walking shoes
Flip-flops/jandals/sandals
Sarong (pāreu – you can buy in the Cook Islands – it’s a good way to cover up when exploring the towns after swimming)
Insect repellent
High-factor sunscreen (that’s reef-safe and water-resistant).

Get more ideas on what to pack with our guide, What to Pack for Rarotonga & the Cook Islands: Cook Islands Packing List.

More About the Weather in Rarotonga and Cook Islands in September

That’s it for our complete guide to the weather and climate in Rarotonga and the Cook Islands in September. Check out the following articles for more weather advice:

Finally, enjoy a comprehensive guide to planning a trip to the Cook Islands in The Best Cook Islands Travel Guide.

Author

Laura S.

This article was reviewed and published by Laura, editor-in-chief and co-founder of Cook Islands Pocket Guide. Since arriving solo in the South Pacific over 10 years ago with nothing but a backpack and a background in journalism, her mission has been to show the world how easy (and awesome) it is to explore a paradise such as the Cook Islands. She knows the islands inside out and loves sharing tips on how best to experience Raro’s must-dos and hidden gems. Laura is also the editor of several other South Pacific travel guides.

Contact Laura via our contact page