Meteorology is the study of the conditions that produce weather patterns. Climatology is similar, but it focuses more on changes over longer periods of time.
Meteorologists particularly look at humidity levels, the temperature and the Earth's atmosphere. They use these conditions to study how weather patterns are produced. They are often interested in major weather events, such as hurricanes, tornadoes and thunderstorms. They use the information they gather to predict future weather patterns and create weather forecasts.
Meteorology really began to develop in the 17th century with scientists and thinkers like Galileo and Rene Descartes, though its origins were much earlier. It was during the 17th and 18th centuries that equipment, such as thermometers, was developed for the study of weather.