How the seasons arise

In short: The seasons arise because the Earth’s axis is tilted by about 23.4 degrees. As a result sunlight strikes the hemispheres at different angles through the year.

In more detail: It is not the distance to the Sun that makes summer and winter. In January the Earth is actually closest to the Sun.

In detail

• Summer: The hemisphere is tilted towards the Sun. Light falls steeply, days are long, it gets warm.
• Winter: The hemisphere is tilted away from the Sun. Light falls at a shallow angle, days are short.
• Solstices and equinoxes: Solstices around 21 June and 21 December, equinoxes around 20 March and 22 September.
• Southern hemisphere: Seasons are opposite there; Christmas falls in summer.
• Polar day and night: Near the poles the Sun stays up for weeks in summer and down in winter (zeitzonen-und-datumsgrenze).