When you're planning your getaway to Gwaunaru'u, be sure to take into account the year-round temperatures. The hottest months are usually April and May with an average temp of 81°F, while the coldest months are November and December with an average of 80°F. The rainiest months in Gwaunaru'u are March, January, February, and December, with each month seeing an average of 19 inches of rainfall.