Why is it cold in winter and hot in summer?

This is because of the angle of the sun.

The temperature of the four seasons depends on the angle and time of the sun. For us, that is, for people in the mid-latitude region of the northern hemisphere, around the "summer solstice", the midday sun shines almost vertically on the ground.

Around the "winter solstice", at noon, the sun shines obliquely on the ground, and the angle of illumination determines how much heat the earth receives, thus causing the temperature to rise and fall. In addition, around the summer solstice, the sun rises in the northeast and sets in the northwest, and the sun stays above the horizon for a long time. This situation of long days and short nights makes the ground in long-term light, which further aggravates the rise of ground temperature;

On the contrary, around the "winter solstice", the sun rises in the southeast and sets in the southwest, and the sun stays above the horizon for a short time. This situation of short days and long nights further aggravated the cooling of the ground. So it is hot in summer and cold in winter.

Extended data

How are the four seasons formed?

There is an included angle (23 26') between the earth's rotation axis and the earth's revolution plane around the sun (ecliptic plane). Therefore, when the earth revolves around the sun, the position of the direct sunlight on the earth will change from 23 26' south latitude to 23 26' north latitude, that is, the tropic of cancer.

When the sun shines directly, the heat and temperature on the earth's surface are high, which is summer; On the contrary, when the sun is tilted, the heat gained on the earth's surface is low, which is winter. When the sun shines directly into the northern hemisphere, it is summer in the northern hemisphere and winter in the southern hemisphere;

On the contrary, when the sun shines directly into the southern hemisphere, it is summer in the southern hemisphere and winter in the northern hemisphere. When the sun shines directly on the Tropic of Cancer, it is the winter solstice (around 65438+February 22nd) and the summer solstice (around June 22nd). When the sun shines directly at the equator, it is the vernal equinox (about March 2 1) and the autumnal equinox (about September 2 1).