In one way or another, most of the energy on Earth originates from the sun. Heat from the sun "powers" all of the major processes in the atmosphere. The heat-trapping greenhouse properties of the Earth's atmosphere and the planet's tilt also play vital roles in weather dynamics and air circulation. Everything about Earth's weather, however, comes back to the sun.
The sun is more than a hundred times wider than the Earth. It is a G2 type star, meaning a yellow star with a mid-range temperature for a star. In the sun's case, this means an average surface temperature of 5,538 degrees Celsius (10,000 degrees Fahrenheit). While the sun produces many types of radiation, the thermal radiation or heat is of most concern to weather systems on the Earth.
The sun does not shine on all parts of the Earth equally, producing uneven heating. This uneven distribution of the sun's heat powers many atmospheric processes. The sun shines most strongly at or near the equator. The light shines weakest on the poles. This makes the equatorial regions much hotter than the polar region. Most heated air and water originates at the equator before flowing elsewhere.
In addition to the temperature differential, Earth's rotation helps move heated air and water around. This creates a complex system of oceanic and air currents. These act as a pump, moving heated air and water away from the equator and colder water and air down from the poles. This helps create many of the Earth's weather patterns, including wind and rainstorms.
Additionally, Earth has a tilt within its orbit, which also changes the way the energy from the sun moves around. In turn, the Northern and Southern Hemispheres take turns "leaning" toward the sun over the course of a year. This causes seasonal variation in the amount of solar energy that creates different temperatures. The tilt of the Earth results in the seasons. For example, when a hemisphere of the Earth is leaning toward the sun, that hemisphere is experiencing summer due to the direction of solar rays.