Records from weather stations in the vicinity of Tabin indicate an average annual total ranging between 150-300 cm. per annum. There are three separate categories for rainfall levels in Tabin with an increasing gradient from south to north. The south-western portion of the reserve, including the peninsula portion, falls within the 150 cm rainfall band along typical of the southern coast of the Dent Peninsula and the District town of Lahad Datu. These areas are within the rain shadow of the high land in central Tabin during the northeast Monsoon. The central portion of Tabin which includes mostly mountainous terrain falls within the 200 cm. band, while the largely low lying northern part of the reserve receives the highest annual average and is within the 250 cm. band. This relatively high rainfall reflects the exposure of the northern area to the northeast monsoon during the early and late months of the year. For southerly areas of the reserve mean monthly rainfall is fairly evenly distributed with highest means in the November-March period. There is a slight peak in July-August but June is generally the driest month. In northerly areas a larger proportion of the annual total falls during the months of December and January. There is a slight peak in May-June and October and the driest month is April.
The fact that humidity remains relatively high in Tabin throughout all months of the year is undoubtedly one of the factors responsible for a comparative absence of fire in the reserve. Evidence of fire has only been found in the north-western area of Tabin (WWFM, 1987).
Mean daily temperatures in the Tabin resort area range from a maximum of 32oC to a minimum of 22oC (Thomas et al, 1976). The hottest month tends to be May when mean daily temperatures of more than 32oC have been observed. The coolest month tends to be February when mean daily temperatures as low as 20oC have been encountered.
The collection long-term climatic data is an important function now being carried out at the Reserve headquarters on a regular basis.
The hilly, forested nature of most sites in Tabin mean that there is usually protection from the wind. As a rainforest area Tabin gets it share of rain but temperatures are tropical and comfortable shelter is near at hand so Tabin can be enjoyed through rain or shine by the properly equipped observer.