Weather, atmospheric condition and climate must be clearly distinguished. Weather describes the current state of the atmosphere surrounding us in a certain place. That means that the weather may change by the day or even at hourly intervals, and that the weather on Earth differs considerably. Our Earth is surrounded by a thick envelope of air which is composed of different layers. This envelope of air is called atmosphere. The weather takes place in the lowest layer of the atmosphere, the troposphere. Due to the Earth’s gravity, it is the densest part of the atmosphere because it contains 80 per cent of the air and almost all gaseous water, which is the moisture bound in the air. The driving force of all weather events and the constantly revolving masses of clouds and air in the troposphere is the sun. Through light and heat radiation the sun provides energy and is like an engine powering our weather. So the foundations of the weather are the warming sunrays, the water in its hydrological cycle and the air which surrounds us with its pressure balancing wind flows that mix and react with one another according to simple physical laws. When these components are available in various amounts, elemental weather phenomena such as fog, clouds, rain, snow, wind, frost and sunshine are formed. The weather often changes daily and sometimes even several times a day and is almost never the same everywhere. So weather is the momentarily perceptible state of the lower atmosphere, the troposphere, in a specific place at a specific time. In the course of a year, the large-scale weather pattern can also remain the same for some days or weeks. Typical characteristics of similar weather are called atmospheric condition.