Taking into account the local weather in Atiu is an important factor for planning your visit, especially if you plan to spend your trip poolside. The hottest months are usually March and February with an average temp of 80°F, while the coldest months are August and September with an average of 75°F. The rainiest months in Atiu are January, March, December, and February, with each month seeing an average of 10 inches of rainfall.