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Although moisture is an important factor affecting precipitation in arid Central Asia (ACA), the water vapour sources and their influencing factors are unclear. This study investigates the moisture sources of extreme precipitation events in summer over Northern ACA and in winter over Southern ACA. The results show that in summer over Northern ACA, the water vapour at low and upper atmospheric levels is mainly transported from the North Atlantic and the Arctic Ocean. In addition, the water vapour in winter over Southern ACA is mainly transported from the North Atlantic and the Northern Indian Ocean. Among these sources, anomalous moisture from the North Atlantic is transported to Northern and Southern ACA along the Mediterranean pressure ridge and the Aral Sea pressure trough. In addition, anomalous moisture in Northern ACA from the Arctic Ocean is closely associated with the negative height anomaly near ACA and with the positive height anomaly in the Mediterranean extending northward to the Arctic Ocean; this results in the high-latitude moisture transporting along the western edge of the cyclone in Northern ACA. In Southern ACA, low-latitude water vapour from the Northern Indian Ocean is affected by negative and positive height anomalies in Northwest and Southeast ACA. In addition, significant ascending motion occurs in the study area which provides the necessary dynamic conditions for precipitation. The precipitation variations in Northern and Southern ACA are also related to sea-surface temperature variations, mainly in the North Atlantic, Arctic Ocean, Mediterranean Sea, and Northern Indian Ocean. Therefore, moisture from the North Atlantic, Arctic Ocean, and the Indian Ocean converge and together influence precipitation development during summer over Northern ACA and in winter over Southern ACA.