September weather forecast
Cook Islands

September in the Cook Islands marks the beginning of a gradual transition from the dry to the wet season. This period sees a slight increase in average temperatures, ranging between 19°C (66.2°F) to 26°C (78.8°F), and a subtle rise in humidity. Despite these changes, the weather remains relatively comfortable for outdoor activities and exploration.

Rainfall in September begins to increase compared to the preceding dry months, although it still remains significantly lower than the wet season levels. The southern islands, such as Rarotonga and Aitutaki, experience rainfall slightly above 100mm (3.94") on average. The northern islands, like Penrhyn and Manihiki, follow suit with a slight increase in rainfall, though they continue to receive less precipitation compared to the southern islands.

September is well outside the South Pacific cyclone season, hence the risk of cyclones remains very low. Nevertheless, as always, it is advised to stay updated with local weather forecasts during your stay.

Comparing September to August, there is a slight increase in both average temperatures and rainfall levels, marking the early stages of the transition from the dry to the wet season. Looking forward to October, these trends continue, with further increases in rainfall and a slight rise in temperature. Thus, September signifies the beginning of a shift in the Cook Islands' climate, moving towards the warmer and wetter conditions of the wet season.

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• Roto - September »
  The month with the least rainfall in Roto is September, when the rain falls for 21.6 days and typically collects 78mm (3.07") of precipitation. June through September, with an average relative humidity of 77%, are the most humid months in Roto.
• Tauhunu - September »
  The month with the least rainfall in Tauhunu is September, when the rain falls for 20.8 days and typically collects 63mm (2.48") of precipitation. In Tauhunu during September, the rain falls for 20.8 days and regularly aggregates up to 63mm (2.48") of precipitation.
• Mapumai - September »
  On the first day of September in Mapumai sunrise is at 06:40 and sunset at 18:24. In Mapumai in September, during 12.6 rainfall days, 30mm (1.18") of precipitation is typically accumulated.
• Avarua District - September »
  The months with the coldest seawater in Avarua District are August and September, with an average sea temperature of 24.5°C (76.1°F). In Avarua District, during September, the rain falls for 5 days and regularly aggregates up to 132mm (5.2") of precipitation.
• Arutanga - September »
  In Arutanga in September, the average water temperature is 26°C (78.8°F). In Arutanga, in September, during 13.4 rainfall days, 31mm (1.22") of precipitation is typically accumulated.
• Omoka Village - September »
  The months with the highest UV index in Omoka Village are January through April, September through December, with an average maximum UV index of 12. Omoka Village's warmest period falls in January, March through July, September through December, when the average high-temperatures ascend to 31°C (87.8°F).
• Mangarei Village - September »
  July through September, with an average sea temperature of 25°C (77°F), are months with the coldest seawater in Mangarei Village. In Mangarei Village, Cook Islands, in September, the average water temperature is 25°C (77°F).
• Oneroa Village - September »
  July and September are months with the least rain in Oneroa Village, Cook Islands, when the rain falls for 5 days and typically aggregates up to 102mm (4.02") of rain. The months with the least rainfall in Oneroa Village are July and September Rain falls for 5 days and accumulates 102mm (4.02") of rain.
• Tautu - September »
  September ushers in the transition from winter to summer in Tautu, with a slight increase in maximum temperatures and longer daylight hours. In Tautu, during September, the rain falls for 13.4 days and regularly aggregates up to 31mm (1.22") of precipitation.
• Nukuao - September »
  On the first day of September in Nukuao sunrise is at 06:36 and sunset at 18:21. In Nukuao, in September, during 12.6 rainfall days, 30mm (1.18") of precipitation is typically accumulated.
• Ngatiarua - September »
  The average relative humidity in September in Ngatiarua is 78%. On the first day of September in Ngatiarua, sunrise is at 06:40 and sunset at 18:24.
• Karanga Village - September »
  On the first day of September in Karanga Village, Cook Islands, sunrise is at 06:40 and sunset at 18:22. A mean low-temperature of 23.1°C (73.6°F) is anticipated during the month of September in Karanga Village, Cook Islands, a slight step down from the daytime high.