Formation of Seasons
The day and night occur by rotation of the earth and the sun; likewise, the seasons occur by revolution. This revolution of the earth is completed in 365 days - 7 days in a week, 30 days in a month and 365 days in a year.
The distance between the Sun and the Earth is different during this orbit (revolution). The part of the Earth which is closest to the Sun is affected by the heat which results to summer season. The part which is away, winters occur there.
The temperature of the Earth changes due to the increasing distance between the Sun and the Earth. A mixture of these two forms the other four seasons. These are called spring, monsoon, autumn and pre-winter.