Over the past 20 years, developing countries have invested in upgrading hydrological and meteorological networks, often with the assistance of development partners. In most of these projects, the share of the investment in the modernization of networks has been between 40 and 50 percent of the total project costs. The objectives of these initiatives have been to create reliable analyses, numerical predictions, and forecasts to inform early action, response, and planning across the whole of society. In some countries, monitoring networks have been sustained and improved over the decades. But in others, maintaining them operationally has remained elusive, resulting not only in inoperable or poorly maintained observational infrastructure and systems but also in a failure to realize the intended benefits. Why did some succeed where others did not That is a question that this report tries to answer by exploring the underpinnings of the successes and the possibilities of replicating these successes elsewhere, and thereby contribute to the body of knowledge on observation networks. This report aims to facilitate the development of more strategic and viable roadmaps for investments in weather and climate observation networks where those investments are likely to be substantial in the coming decades, as countries improve resilience to natural hazards and economies transform in response to climate change challenge.