There are three states which comprise Malaysia; Peninsular Malaysia (the "mainland" immediately North of Singapore), and the East Malaysia states of Sarawak and Sabah on the island of Borneo. Thus Malaysia is divided geographically between the peninsula and the island of Borneo, over half of which is the Indonesian state of Kalimantan. Peninsular Malaysia is strongly affected by the same dual monsoon seasons as Thailand, with the higher central mountain range creating distinct seasons on the two coasts.
Diving is best on the East coast from April through October, while the West coast is visited by divers from November to March. On the east coast of Sabah on the island of Borneo, the dive season runs throughout the year, though monsoon rains from December to March can at times curtail diving activities. However, at that time of year the crowds are down and some travellers find it the best time to go for that reason.
Weather patterns on the west coast of Sarawak on Borneo (Labuan and Kota Kinabalu) follow those on the east coast of peninsular Malaysia, with the low season being November to March. Note this also includes Layang Layang Resort out in the South China Sea. For further information on diving refer to: