When is the warmest during the day?

At noon, the sun is perpendicular to the earth, therefore, its rays have the shortest path, which means that the earth receives more heat than, say, in the morning. But heat depends not only on how hot the earth is, but also on how hot the air is. It takes time for the heat absorbed into the earth to heat it up. So it turns out that the peak falls a few hours after noon, when the air has already warmed up, and the earth has not had time to cool down.