Understanding the rainfall patterns in northern Thailand is crucial for national water management since they affect several of Thailand’s major rivers. This study aims to understand the trends of climatic variations in northern Thailand over the past 64 years (1951-2014). Pre- and post-monsoon rainfalls are considered to assess temporal Southeast Asian monsoon (SEAM) transition. Finally, multi-decadal oscillations of the rainfalls were evaluated using the Holt-Winters seasonal time-series analysis and their associations with the biennial oscillation, El Niño Southern Oscillation (ENSO), Indian Ocean Dipole (IOD), MaddenJulian Oscillation (MJO), and the Schwabe-Hale cycle were also discussed. The results showed a climatic trend toward earlier coming of the SEAM rainfall. The time-series and linear correlation analyses revealed that the ENSO, MJO, and solar irradiance influenced the rainfalls differently in the pre- or post-SEAM or both and they were also related to the periodicities of the extreme rainfall events. However, the IOD did not directly influence the local SEAM rainfall but it co-occurred with the ENSO.
