According to reports, the number of affected residents in the flooding in Maguindanao del Sur rose to 1,92,005 as of 1700 hours on Monday (19 May), as per the National Disaster Risk Reduction and Management Council (NDRRMC).

• The number of affected barangays include those in the towns of Ampatuan, Datu Abdullah Sangki, Datu Piang, Datu Salibu, Datu Saudi Ampatuan, Datu Hoffer Ampatuan, Mamasapano, Guindulungan, Shariff Aguak Shariff Saydona Mustapha, and Sultan sa Barongis.
• The NDRRMC added that the marshy town of Mamasapano has the highest number of affected residents with 34,700.
• On Tuesday (20 May), the Philippine Atmospheric, Geophysical, and Astronomical Services Administration released a flood advisory for Bangsamoro, particularly in the provinces of Basilan, Lanao del Sur, and Maguindanao provinces, as heavy rainfall due to the low-pressure area may affect the area.
• The State weather bureau noted that heavy rainfall could likely affect waterways, particularly in Barangay Nituan in Parang, Maguindanao del Norte; the river systems in Datu Odin Sinsuat and Buluan and Matuber in Datu Blah Sinsuat, and rivers and tributaries in Dapao in Pualas and Matling in Malabang, all in Lanao del Sur; and the rivers in Gubuan and Kumalarang in Basilan.
• People living near the mountains slopes and in the low-lying areas of the above-mentioned river systems and the local disaster risk reduction and management councils concerned are advised to be alert for possible flashfloods.