The four seasons, Spring, Summer, Autumn and Winter each happen once a year.
Many people think that it is colder in the Winter because the Earth is further away from the Sun, but this is not true. In fact, when it is winter in Europe it is summer in Australia so somewhere on Earth when it is winter, it is summer on the other side of the planet.
In the Northern Summer, the Northern part of the Earth is tilted towards the Sun. This means that the Sun is higher in the sky in the middle of the day. This makes it hotter.
In the Northern Winter, the Northern part of the Earth is tilted away from the Sun, so the Sun does not get as high in the Sky and it is, therefore, much colder.
To find out more about the tilt of the Earth and how this causes the seasons follow this link.
To carry out a short experiment to see this for yourself click here.