The Philippines is ranked fourth after the United States, China and India as the countries with the highest number of disasters over the past 20 years (UNODRR and CRED 2015). According to a study undertaken by the World Bank and the Philippine's National Disaster Coordinating Council, in direct damages, these hazards cost the government an average of P15bn per year, which is often more than 0.59% of the national GDP. The cost further increases if indirect and secondary impacts are considered. There is also a considerable number of social and environmental impacts associated with these disasters. Of all the disasters experienced in the Philippines, flooding is the most frequent. Many dramatic flood events have been recorded since historical times. Metropolitan Manila has also been indicated as the most flood prone area in the country. Marikina City, which is one of the sixteen cities in Metropolitan Manila, is not exempted from the flooding impacts faced by the metropolis. Flooding in the city is reported to be historical with some writers linking it to the 1980s when impacts started to be felt. The city, after realizing the devastating impacts from a flood event caused by typhoon Ondoy in September 2009, decided to embark on impact reduction measures. An Early Warning System was then implemented in 2012. By considering the potential increase in impact due to climate change and non-climatic factors (such as increasing population, infrastructure), the study intends to evaluate the early warning system and provide recommendations for its improvement. The research concentrated on Barangay Tumana as a case study since it is identified by the Marikina City Disaster Risk Reduction and Management Office as the most vulnerable barangay.