The rainy season occurs in countries with tropical and subtropical climates, causing these regions to experience frequent high rainfall throughout the year. Extreme precipitation in certain countries is influenced by their geographical features and unique climate patterns. Areas located along monsoon routes or those with mountainous terrain tend to receive more intense rainfall than others. According to the World Meteorological Organization, extreme rainfall has triggered major flooding across several parts of South and Southeast Asia, resulting in hundreds of deaths, mass evacuations, and significant economic losses.

Asia is one of the regions most vulnerable to flooding as the impacts of climate change continue to intensify. Rising global temperatures increase the likelihood of extreme rainfall because warmer air can hold more water vapor. Citing World Atlas, here are the 10 countries with the highest average annual rainfall:

1. Colombia: 3,240 mm

2. Sao Tome & Principe: 3,200 mm

3. Papua New Guinea: 3,142 mm

4. Solomon Islands: 3,028 mm

5. Panama: 2,928 mm

6. Costa Rica: 2,926 mm

7. Samoa: 2,880 mm

8. Malaysia: 2,875 mm

9. Brunei: 2,772 mm

10. Indonesia: 2,702 mm

High Rainfall in Indonesia
According to BMKG, heavy to very heavy rainfall has the potential to occur across southern parts of Indonesia, including Java, Bali, West Nusa Tenggara, East Nusa Tenggara, South Sulawesi, and southern Papua. This condition highlights the need for several regions to stay alert to severe rainfall and related natural hazards.

From February to April 2026, most Indonesian regions are expected to experience moderate rainfall and gradually return to normal conditions. However, from November to December 2025, many areas will likely face above-normal rainfall, especially North Sumatra, North Kalimantan, North Sulawesi, and North Maluku. Global and regional factors, including weak La Niña and a negative Dipole Mode (-1.61), keep atmospheric conditions unstable and support the formation of convective clouds. This increases the risk of heavy rain and strong winds, particularly in North Sumatra, West Java, Central Java, Yogyakarta, East Java, Banten, West Nusa Tenggara, and South Sulawesi.

BMKG has also detected Tropical Cyclone Kalmaegi in the southwestern Indian Ocean near Lampung, along with other cyclonic circulations that influence national weather patterns. For the week of November 3–9, 2025, moderate to heavy rainfall is expected in areas such as the western coast of Sumatra, much of Java, Bali, Nusa Tenggara, Kalimantan, Maluku, and Papua. BMKG, together with BNPB and other agencies, has carried out Weather Modification Operations (WMO) in several high-risk regions, including:

• Central Java (Semarang & Solo posts) using two aircraft—Cessna and Grand Caravan—on October 25–November 3, 2025.

• West Java (Jakarta post) operating one aircraft on October 23–November 3, 2025.