The weather is the state of the atmosphere, as defined by various weather elements, for a specific place and time. Weather refers to short-term (minutes to weeks) variations in the atmosphere. Climate on the other hand is usually defined as the average weather for a particular place and is described in terms of the mean and variability of the weather elements over a long time period. The classical period is 30 years, as defined by the World Meteorological Organization (WMO).