Weather is probably a major factor when you plan your trip to Cocos Island, and keep 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 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.