If you’re hoping to get lost in the rain on your romantic getaway, take a look at these details about year-round temperatures in Green Island: The hottest months are usually August and September, with an average temperature of 28°C, while the coldest months are February and January, with an average of 26°C. The rainiest months in Green Island are May, October, September and August, with each month seeing an average of 214 mm of rainfall.