Why isn't the day when the sun shines directly on the Tropic of Cancer the hottest day of the year?

Theoretically, the temperature should be the highest when the sun is in direct sunlight, but in fact it is not. For example, the sun shines directly on the Tropic of Cancer from summer to morning, but the hottest time in the northern hemisphere is not around summer, but there is a delay of 15 ~ 20 days.

This is mainly due to the effect of heat storage and heat release in the near-surface layer and atmospheric circulation.

atmospheric circulation

In the mid-latitude region of the northern hemisphere, first of all, the heat in the surface layer did not reach its peak from summer to around, and it continued to accumulate at this time. When it doesn't reach the maximum value, it won't reach the maximum value until about 15 from summer to the future. Second, the sun will heat the cold air in the north, and the heated cold air will go south from the north until the summer 15 ~ 20 days later, which is also the time when the ground temperature in the mid-latitude area in the northern hemisphere is the highest. Therefore, the highest temperature in the northern hemisphere is1summer solstice after 5 ~ 20 days.

This is my understanding, not necessarily correct.