5 days worth of rain in 1 hour: ‘Extreme’ rainfall overwhelms Quezon City’s drainage system

A record-breaking downpour hit Quezon City on Saturday, causing floods that quickly submerged several areas and took officials by surprise.

According to data from the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA), the powerful thunderstorm dropped a staggering 141 millimeters of rain in one day, an amount equivalent to five days' worth, with the most intense period delivering 121 mm in just a single hour. This intensity surpasses the peak hourly rainfall of 90 mm recorded during Typhoon Ondoy in 2009.

Scientific analysis of the August 2025 Quezon City floods

A social media post offered a detailed and accessible analysis of the August 2025 Quezon City floods, based on scientific findings from the UP Resilience Institute. The post explains that the analysis integrates meteorological data, urban planning insights, and climate resilience principles to provide a comprehensive understanding of the event.

Drainage systems were 'overwhelmed'

Officials from the Quezon City Disaster Risk Reduction and Management Office (QCDRRMO) admitted that the city's drainage system was overwhelmed by the sudden deluge. The 'very localized' weather event caused severe flooding in 36 of the city’s barangays, including areas not typically prone to floods.

The flooding, however, receded within a few hours, a sharp contrast to the extended inundation caused by Typhoon Ondoy in 2009.

The city government is continuously conducting cleanup operations to clear debris and silt left by the deluge.

Experts warn of 'extreme' weather events

In a post on Saturday, Project NOAH Executive Director Mahar Lagmay called the downpour 'extreme,' saying it was far more intense than the usual heavy rains.

'Most of that 141 millimeters recorded in Quezon City fell within just one hour, between 2 and 3 p.m.,' he wrote. 'This wasn’t just torrential rain, which is 30 to 60 millimeters per hour. This was extreme — more than 60 millimeters an hour. I never thought I’d experience something like it.'

Dr. Lagmay suggest that extreme weather events of this nature are becoming more common due to climate change. He said the UP Resilience Institute is assisting the Quezon City government with a new Drainage Master Plan to guide long-term flood mitigation.

As the rainy season continues, authorities are urging the public to stay alert. The recent flooding serves as a powerful reminder for the need for better infrastructure and urban planning to address the escalating effects of climate change.