Extreme weather events and natural disasters such as drought or floods can have a devastating impact on food security as well as the social and economic development of rural households. In recent years, an increasing number of initiatives have tested weather index-based insurance to help manage these risks in agriculture. Building on the experience of the IFAD-WFP Weather Risk Management Facility (WRMF) and the analysis of 37 index insurance programmes around the world, this paper identifies eight key principles to help weather index-based insurance reach scale and sustainability. It also includes nine case studies on index insurance programmes and outlines how donors and governments can support the sector.