Mass flowering has been identified in dipterocarp forests in the aseasonal tropics. The role of resource availability as one of the proximate factors for intermittent and synchronized flowering has attracted much attention with strong theoretical support. On the other hand, it has long been disputed whether external environmental cues would be sufficient to explain mass flowering. To explore key factors that regulate floral initiation in Dipterocarps, we analyze long-term flowering phenology data of six Shorea species together with climate data monitored in Pasoh forest reserve in peninsula Malaysia using generalized linear models. The result of model analysis and model selection showed that most of species integrate chilling and drought signals to initiate flowering, implying that they flowered when both signals occurred. The estimated timing of floral initiation was the same between species, and the estimated periods required for flower development showed the exactly same order of sequential flowering previously reported by Ashton et al. (1988). There results provide important implications to predict phenological responses of tropical tress to future climate change.