Between mid-October and the end of March the climate at the eastern side of the peninsula is affected by the rainy season or monsoon season. Weather usually is very rough in these months, for this reason it is not the best time to visit these parts of Malaysia. There are some tropical islands (i.e. Perhentian, Redang and Tioman) that 'close' during the monsoon period. This means that resorts are closed, and ferries and boats do not bring tourists to the islands. During the monsoon period it can sometimes rain for days. This doesn't mean that you should avoid Malaysia during these months. All other parts of Malaysia are not affected by this monsoon, for example Penang, Langkawi and many other places on the western side of the peninsula are perfect for a visit. Same goes for Borneo.