Why does the lowest temperature appear geographically (before and after sunrise)?

Sunlight raises the temperature. Without sunlight, the heat in the air will gradually dissipate outside the earth with the thermal movement of air molecules.

After the sun went down, the temperature gradually dropped. If the sun doesn't rise, the surface temperature of the earth will continue to drop. But the next morning, the sun will rise again, and under the irradiation of sunlight, heat will gather in the air again, raising the temperature. Therefore, before sunrise, it is the lowest temperature in a day. Due to the refraction of light by air, when we see the sun from the horizon, the sun has not actually risen, but is still below the horizon.