Extremely heavy rainfall from super typhoon Koppu has caused deadly flooding and mudslides in the Philippines. Koppu hit the eastern coast of Luzon as a category four super typhoon with winds of 130kts (150 mph). Koppu weakened but was still battering the Philippines as a typhoon after reaching the Lingayen Gulf on Luzon's western coast. Typhoon Koppu then made a turn toward the north and continued to drench the northern Philippines as it followed Luzon's northwestern coast. Torrents of rain flowing from mountainous terrain magnified the effects of very high rainfall totals.

A rainfall analysis was performed using NASA's Integrated Multi-satellitE Retrievals for GPM (IMERG) data. Those data showed that most of the island of Luzon was covered by very heavy rainfall from typhoon Koppu. This analysis indicates that most of the island of Luzon received over 300 mm (11.8 inches). Some areas near the typhoons path were shown to be saturated with over 760 mm (about 30 inches) of rainfall.

As a tropical storm Koppu moved into the Luzon Strait and is predicted to continue weakening while moving away from the Philippines.