Weather will likely play an important role when you plan your trip to Cocos Island, but bear in mind that cheaper options are usually available when the weather isn't as good. The hottest months are usually April and May, with an average temperature of 29°C, while the coldest months are August and July, with an average of 28°C. The rainiest months in Cocos Island are January, February, March and December, with each month seeing an average of 436 mm of rainfall.