Weather
Weather is the state of the atmosphere at a particular time, as defined by the various meteorological elements, including temperature, precipitation, atmospheric pressure, wind and humidity.
Overview
Weather describes short term events and differs from climate, which describes the average weather conditions for a particular location, over long periods of time, usually years or decades. For example, to obtain information about typical climate conditions a climatological standard normal is computed using data for a period of 30 years.
Weather is an hourly, daily phenomenon that affects every aspect of our lives. Therefore, we need weather forecasts to know what to wear, to plan our day and to prepare for the weather-related hazards that may lie ahead.
Weather forecasts provide essential information to support decision-making in many areas, including:
• safe transportation on land, by sea and in the air,
• freshwater resources management,
• sport, adventure and tourism,
• agriculture, building infrastructure and energy management,
• taking lifesaving, timely action in the face of impending natural hazards such as tropical cyclones, floods, etc.
An extreme weather event is rare at a particular place and time of year, with unusual characteristics in terms of magnitude, location, timing, or extent. The characteristics of what is called extreme weather may vary from place to place in an absolute sense. Examples of extreme weather include, but are not limited to, heatwaves, cold waves, heavy precipitation, drought, tornadoes and tropical cyclones.
Impact
Weather might refer to sunshine, rain, snow, hail, sleet, mist, blizzards, storms, and similar phenomena.
Extreme weather events can have serious impacts on society, including loss of life, damage to infrastructure, and destruction of ecosystems. These adverse impacts are amplified by the increased intensity, duration and spatial extent of extreme weather events in the past decades. Sequential extreme events can compound increasing impacts above what would normally be expected for an isolated extreme weather event.
Natural climate variability can result in weather extremes, but climate change is leading to changes in the frequency, intensity, spatial extent, duration and timing of weather and climate extremes.
More frequent and more intense weather events, such as severe heatwaves, and heavy precipitation lead to increased impacts on more vulnerable populations.
WMO's response
WMO coordinates the worldwide efforts that are a prerequisite to produce accurate and timely weather forecasts.
WMO works with Members and their National Meteorological and Hydrological Services to coordinate the global network of Earth system observations, free and open exchange of data, continuous research, and global, regional and national data-processing for numerical weather prediction - all required to deliver accurate, timely weather forecasts and services. This data and information can help to inform early warning systems so that people can take action to mitigate disasters before they happen.
Each contribution counts and improves the weather forecasts. The results are far greater than the sum of its parts and could not be achieved by any one Member on its own.
WMO has contributed to the implementation of Early Warning Systems to protect people and livelihoods since its establishment. It is now co-leading international efforts through the United Nations Initiative “Early Warnings for All by 2027” to strengthen Earth system observations and monitoring, predictive and warning capabilities in every region globally.
WMO presides over the World Weather Information Service, which presents weather observations, weather forecasts and climatological information for selected cities supplied by National Meteorological & Hydrological Services (NMHSs) worldwide.
WMO also presides over the Severe Weather Information Centre. The website is based on advisories issued by Regional Specialized Meteorological Centres and Tropical Cyclone Warning Centres, and official warnings issued by National Meteorological and Hydrological Services for their respective countries or regions.
