There has been an increasing concern about the effect of climatic change on human health in recent years. It has been suggested that young children are particularly at risk due to the reduced regulating mechanism against extreme climatic changes. However, few studies on the associations between climatic factors and childhood illness, specifically among young children, have been found in the literature. This epidemiological study utilized data collected on all young patients aged less than 6 years who presented to an emergency department for a period of two years. Information on climate and outdoor air quality variables was obtained from the Bureau of Meteorology. Data were analysed with various ARIMA time series models for each common childhood illness. Results suggested that maximum daily temperature was a significant risk factor for fever (t = 5.29, p < 0.001) with a regression coefficient of 0.37 (SE = 0.07) and gastroenteritis (t = 2.69, p = 0.007) with a regression coefficient of 0.10 (SE = 0.04). The UV index was also found to be significantly but negatively related to gastroenteritis (t = -2.37, p = 0.018). However, none of the climatic variables were associated with respiratory problems after adjusting for other air quality variables and infectious disease.