Why does the highest temperature appear around 14 and the lowest temperature appear every day?

Diurnal variation characteristics of temperature: the highest value is not at noon 12, but around 2 pm. Because solar radiation reaches its maximum at noon, it radiates to the ground, but the ground is the main heat source of the atmosphere, so generally speaking, it is the hottest at 2 pm.

The lowest value is not at midnight, because there is no solar radiation heating, and the ground radiation gradually weakens until the lowest before sunrise the next day. So in general, the temperature is the lowest before and after sunrise.