If you’re looking forward to lots of outings with your partner, take a look at these details about year-round temperatures in Sibu: The hottest months are usually May and August, with an average temperature of 27°C, while the coldest months are February and March, with an average of 26°C. The rainiest months in Sibu are December, January, November and October, with each month seeing an average of 340 mm of rainfall.