Background The Mekong Delta is the most vulnerable region to climate change in South-East Asia; however, the association between climate and children's health has rarely been studied in this region.

Objective We examined the short-term association between daily temperature and hospital admissions for all causes, gastrointestinal and respiratory infection, among young children in the Mekong Delta area in Vietnam.

Methods Daily paediatric hospital admissions and meteorological data were obtained from January 2008 to December 2012. A time-series approach was used with a combination of a Poisson regression and constrained distributed lag models to analyse the data. The long-term and seasonal trends, as well as other time-varying covariates, were adjusted using spline functions. Temperature—pediatric admission relationship was evaluated by age-specific (0–2 and 3–5-year-olds) and cause of admission groupings.

Results A 1°C increase in the 2-day moving average temperature was significantly associated with a 3.4% (95% CI 1.2% to 5.5%), 4.6% (95% CI 2.2% to 7.3%), 2.6% (95% CI 0.6% to 4.6%), 4.4% (95% CI 0.6% to 8.2%) and 3.8%(95% CI 0.4% to 7.2%) increase in hospital admissions with 0–2-year-old children, 3–5-year-old children, all causes, gastrointestinal infection and respiratory infection, respectively. The cumulative effects from 1-day to 6-day moving average temperature on hospital admissions were greater for 3–5-year-old children and gastrointestinal infection than for 0–2-year-old children and other causes.

Conclusions Temperature was found to be significantly associated with hospital admissions in young children with the highest association between temperature and gastrointestinal infection. The government agencies of Mekong Delta should implement measures to protect children from the changing temperature conditions related to climate change.