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Droughts have caused damage to regional agriculture in western China. The standardized precipitation index (SPI) and standardized precipitation evapotranspiration index (SPEI), widely used around the globe, are employed here to increase our understanding of the drought indices, spatiotemporal characteristics, and factors related to agricultural droughts in western China; this is important for water resource management and drought forecasting in the region. Results show that both the SPEI and SPI can monitor typical agricultural droughts, but some differences appear against a background of climate change. The SPEI can generally accurately reflect variations in soil moisture in humid regions, while the SPI shows a better performance in other climate zones. Three spatially well-defined sub-regions with different temporal evolutions of droughts were identified to explain the main dry/wet variations across western China. Large-scale circulation patterns, daily extreme precipitation, daytime heatwaves, and geographic factors were found to have a potential connection with droughts. [ABSTRACT FROM AUTHOR]