The World Meteorological Organisation (WMO) is a specialized international agency of the United Nations with the aim of gathering, analysing, standardizing and disseminating international meteorological observations and improving the exchange of information. Its establishment was agreed in 1947 as a successor to the International Meteorological Organization, it came into being in 1951, and later in 1951 it became a UN agency. It has 185 members (179 member states and 6 dependent territories).

Its chief activities are the World Weather Watch programme, which coordinates facilities provided by member states, and a programme that aims to extend knowledge of the natural and human-induced variability of climate. It also encourages research and training; standardizes observations and ensures their uniform publication; and furthers the application of meteorology to aviation, shipping, agriculture, and other human activities. Its headquarters are in Geneva.

Data from all over the world are needed to provide weather forecasts. If there were no WMO, the nations of the world would have to conclude individual agreements with one another to ensure the exchange and availability of data to meet their national requirements, such as provision of forecasts for the public and special services for various economic sectors like agriculture, utilities (gas, electric power production) and so on. An aircraft does not take off, nor does a ship leave port, without a weather forecast. The provision of such services is part of the international responsibilities of individual countries which would be hard pressed to provide accurate and timely information if the global infrastructure established under the auspices of WMO did not exist.