Weather is the conditions of the atmosphere at a particular place and time, such as temperature, precipitation, humidity, and wind. It can change from day to day, and even hour to hour. Some common types of weather include sunshine, rain, snow, sleet, hail, fog, and thunderstorms. Weather is caused by many different factors, such as the temperature and moisture of the air, the movement of the air, and the presence of hills, mountains, and other geographical features. People who study weather are called meteorologists, and they use special instruments and tools to measure and predict the weather. Weather can have a big impact on our daily lives, from what clothes we wear to what activities we can do outdoors.