Climate, the average condition of the weather in an area for a period of years. Weather, on the other hand, is the condition of the atmosphere at a particular time and place. In order to describe the climate of a given region, monthly and seasonal averages are made of rainfall and such properties of the atmosphere as temperature, humidity, pressure, and wind velocity.

Climate has a major effect on human activities. What people eat and wear, as well as how they earn their livelihoods, all depend to some extent on the local climate. A drastic change in a region's climate has sometimes contributed to the migration of large groups of people.