Weather and climate
Also called: Elements of weather and climate · Topic: Atmosphere: Composition, Structure and Elements of Weather · NCERT: Class 11, Ch 4 "Climate"; Class 11, Ch 6 "Natural Hazards and Disasters: Causes, Consequences and Management"; Class 11, Ch 7 "Composition and Structure of Atmosphere"
Meaning
Weather is the state of the atmosphere at a given place and time. It changes fast, within hours or days. Climate is the average weather over a large area and a long period, usually 30 years or more, and it changes very slowly. The WMO calls this 30-year average a "normal". The current normal is 1991–2020. Both are described by the same elements: temperature, pressure, wind, humidity, clouds and precipitation. Seasons sit between the two, and IMD recognises four of them.
Example
"It is raining in Delhi today" describes weather. "Delhi has a hot semi-arid to humid subtropical climate" describes climate. One unusually cold winter in Delhi does not change its climate, because climate looks at the long-term average.
Don't confuse with
- Season: a part of the year with a typical weather pattern, such as the monsoon. It is longer than weather but much shorter than the 30-year span used for climate.