The Earth travels around the sun one full time per year. During this year, the seasons change depending on the amount of sunlight reaching the surface and the Earth’s tilt as it revolves around the sun. Summer occurs when a hemisphere is tilted towards the sun, and winter occurs when a hemisphere is tilted away from the sun.
When it is summer in the northern hemisphere, it is winter in the southern hemisphere. At the equator, there are no seasons because the sun is always striking and the temperatures remain high there. In general, the summer and winter temperatures get low er the further away from the equator.