There are numerous drought indices that must be continuously monitored to determine the beginning and end of drought events and their spatio-temporal characteristics. This paper describes and compares the performance of six indices for drought monitoring based on rainfall data in southern South America, with the aim of obtaining the most suitable index for the analysis of droughts in the region. The analyzed indices are the standardized precipitation index, the lack of rain index, the deciles index, the effective drought index, the percentage of normal precipitation and the Z-score. These indices were calculated at multiple time scales, which allow evaluating different types of droughts. Five relevant criteria, such as sensitivity, dimensionality, transparency, flexibility, and tractability, were evaluated. Through the analysis of its statistical properties and its evaluation of the spatio-temporal behavior, we found that the standardized precipitation index is the most suitable for the study and monitoring of meteorological droughts in southern South America. The results of this comparison allowed us to establish a set of recommendations
about the analyzed drought indices, which mainly focus on their categorizations and theoretical aspects.

Keywords: drought indices; meteorological drought; drought monitoring; Southern South America; precipitation.