Seasonal Rainfall Variation in Sabah and Sarawak

The seasonal variation of rainfall in Sabah and Sarawak can be divided into five main types:

(a) The coastal areas of Sarawak and northeast Sabah experience a rainfall regime of one maximum and one minimum. While the maximum occurs during January in both areas, the occurence of the minimum differs. In the coastal areas of Sarawak, the minimum occurs in June or July while in the northeast coastal areas of Sabah, it occurs in April. Under this regime, much of the rainfall is received during the northeast monsoon months of December to March. In fact, it accounts for more than half of the annual rainfall received on the western part of Sarawak.

(b) Inland areas of Sarawak generally experience quite evenly distributed annual rainfall. Nevertheless, slightly less rainfall is received during the period June to August which corresponds to the occurence of prevailing southwesterly winds. It must be pointed out that the highest annual rainfall area in Malaysia may well be found in the hill slopes of inland Sarawak areas. Long Akah, by virtue of its location, receives a mean annual rainfall of more than 5000 mm.

(c) The northwest coast of Sabah experiences a rainfall regime of which two maxima and two minima can be distinctly identified. The primary maximum occurs in October and the secondary one in June. The primary minimum occurs in February and the secondary one in August. While the difference in the rainfall amounts received during the two months corresponding to the two maxima is small, the amount received during the month of the primary minimum is substantially less than that received during the month of the secondary minimum. In some areas, the difference is as much as four times.

(d) In the central parts of Sabah where the land is hilly and sheltered by mountain ranges, the rainfall received is relatively lower than other regions and is evenly distributed. However, two maxima and two minima can be noticed, though somewhat less distinct. In general, the two minima occur in February and August while the two maxima occur in May and October.

[ Back ]