Why is the weather always high during the day and low at night?

This is the same as equatorial heat and polar cold. That is, the daytime is similar to the equator, and the light density across the sun on the ground is large, so the heat generated is concentrated and the temperature is high; At night, similar to the poles, the light density across the sun on the ground is small, so the heat generated is dispersed and the temperature is low. So the temperature is higher during the day than at night.