Climate is usually described in terms of the familiar elements of the weather. Temperatures and precipitation (rain, sleet, snow and hail) are the essential indicators, but others include sunshine, wind, cloud cover, atmospheric pressure and humidity. When these elements are measured systematically at a site over a period of several years, we eventually accumulate a record of observations from which we can construct an accurate summary of the climate of that location. Using a variety of statistical techniques, we can compute averages for different climate elements as well as measures of variability and the frequency of occurrence of more extreme events.
Information from climate stations within one country can allow a picture of regional climate to be built up. Sometimes scientists bring together data from all over the world to study the climate of the whole Earth, for example when investigating global climate change.