Planning for the weather is a good way to make your trip to Cocos Island relaxing and enjoyable, especially when you're splurging. The hottest months are usually April and May with an average temp of 84°F, while the coldest months are August and July with an average of 82°F. The rainiest months in Cocos Island are January, February, March, and December, with each month seeing an average of 17 inches of rainfall.