Assessment of rainfall for September 2023 showed that rainfall anomalies in most parts of the ASEAN region are within the near-normal range (50 to -50 mm). However, positive rainfall anomalies (50 to 150 mm) were observed over the southwestern and southern Philippines, northern Thailand, southern Myanmar, southern Cambodia, the southern extremes and central part of Vietnam, northeastern Brunei, and in the northern extreme of the West Papua island of Indonesia.

Furthermore, the northern parts of Myanmar, Vietnam, Laos, and Cambodia, the northeastern Philippines, and several regions of Indonesia including southwestern West Papua and Kalimantan islands, southeastern Sumatra, Sulawesi, and Banda islands are within the negative rainfall anomalies (-50 to -150 mm).