Purpose Water is a basic human right that is still not ensured for many people worldwide. Essential for human health and development, water security is an increasingly important area for social welfare research. At the household level, a common water security proxy is access to an improved source of drinking water such as piped water, a public tap, or a protected well. In urban areas of developing countries, however, recent research has identified important household disparities that regional and national statistics on improved access can mask. To extend these analyses, this study examines seasonal differences in household water security-an emerging priority area due to urbanization, population growth, and environmental change trends. Methods Data are from randomly sampled household surveys (N =396) in Baguio City, the Philippines, on water quantity, quality, and accessibility in dry versus rainy seasons. Bivariate and principal component analyses were performed. Results Water quantity and accessibility are lower in the dry than rainy season for several measures, typically with a wide range among households. Water quality is rated somewhat higher in the dry than rainy season. Principal component analysis yields a multidimensional measure of dry season hardship and no comparable rainy season measure. Conclusions Important heterogeneities of seasonal water security exist among households in this study. More rigorous documentation of local inequities is needed, incorporating seasonal aspects of water security that are appropriate for local contexts.