When does the lowest temperature appear in a day?

The lowest temperature in a day appears at 6 o'clock.

The lowest temperature in a day usually appears around sunrise, which is around five o'clock. 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. Because of the refraction of light by air, when the sun is seen from the horizon, it does not actually rise and is still below the horizon. So when the sun just rises, it is also the lowest temperature.