The potential effect of such extreme weather was shown in 2011 when Thailand was hit by the worst flood it had experienced in 50 years. This study produced the first comprehensive estimate of the economic losses experienced by households that were badly affected by the 2011 Bangkok flood. The study finds that the median household economic cost of the 2011 Bangkok floods was equivalent to about half of an average household’s annual expenditure. It highlights a number of factors that exacerbated the cost of the floods and calls into question the effectiveness of the city’s early warning information systems. It recommends that the flood-warning information provided to households should be carefully designed so that it allows people to make informed choices about how to act. These findings provide important information for the Government of Thailand, which is currently considering which approaches to take to protect people and property from floods and to reduce the economic losses that floods cause.