A five-day weather forecast today is generally as reliable as a three-day forecast two decades ago. Outlooks of up to a week, especially in temperate mid-latitude regions are becoming increasingly reliable. Information can be disseminated around the world from one location to another within three hours, while recently understood phenomena such as El Niño Southern Oscillation (ENSO) (El Niño, La Niña and neutral phases) can be forecast up to a year in advance. Seasonal climate predictions can be forecast up to a month, three months or six months ahead although these climate predictions are probabilistic in nature. Such forecasts, often from more advanced centres, are made available globally to all nations.

Air pressure, temperature, mountain ranges, ocean currents and many other factors combine to produce an enormous quantity of interacting variables all of which can alter the weather to a greater or lesser extent. However, greater understanding of the science, plus the use of powerful computer models, continue to improve our ability to make more accurate predictions with longer lead times.

Every year, natural disasters affect many communities around the world, leading to the loss of lives, the destruction of social and economic infrastructure and the degradation of already fragile ecosystems. Such hazards are inevitable and can threaten everyone, but they tend to hit communities in developing and least developed countries the hardest, increasing their vulnerability and setting back their economic and social goals, sometimes by decades.
While economic losses in dollars for developing countries are lower than those for developed countries, impact (as a percentage of GDP) is often much higher. Many developing nations lie in tropical zones where extreme weather events such as tropical cyclones, droughts and flooding are more frequent than in other regions. Developing nations possess limited facilities and qualified human resources to monitor and predict these phenomena and provide warnings to all sectors of the population. Addressing this challenge is a major concern for WMO.

Experiments on weather modification have been, and continue to be, carried out. The most prevalent method is cloud seeding, which dates back to 1946 and is the attempt to alter the amount or type of precipitation produced by clouds. This is done by targeting clouds from aircraft or from the ground with substances such as silver iodide, dry ice and even salt. In the 1950s and 1960s, US scientists experimented in modifying tropical cyclones (Project Stormfury) but the research was inconclusive.
Today, cloud seeding is employed in many countries in an effort to increase precipitation in drought-stricken areas, reduce the size of hailstones that form in thunderstorms, reduce fog around airports and even to provoke snow at major ski resorts. However, the impacts of operations in rainfall enhancement and hail suppression have still not been properly quantified and modification remains an area of active research.