Taking into account the local weather in Sungai Sumun can help you maximize your time at the pool during your trip. The hottest months are usually July and June with an average temp of 81°F, while the coldest months are January and February with an average of 79°F. The rainiest months in Sungai Sumun are November, December, October, and May, with each month seeing an average of 11 inches of rainfall.