Limit of heat, meaning "heat out", high temperatures will gradually fade. After the limit of heat, the direct solar point continues to move southward, the solar radiation weakens, and the subtropical high withdraws southward. As the sun‘s altitude continues to decrease, the heat brought by it also weakens. limit of heat means the end of the torrid weather, during which the weather is still hot but on a downward trend. The summer heat is a slow process, and it is not cool immediately after the summer heat drops, but it is generally cool after the white dew.

Limit of Heat began to affect China‘s cold high pressure, under its control, the formation of sinking, dry cold air, first announced the end of the rainy season in northeast China, North China and Northwest China, and took the lead in the most beautiful weather of the year autumn crisp.

After the Limit of Heat, the temperature drops gradually, and the temperature difference between day and night gradually increases, but the daytime temperature is still high. The reason for this phenomenon is that the direct point of the sun continues to move south, and the solar radiation is weakened; Second, the subtropical high is retreating to the south by leaps and bounds, and the Mongolian cold high is beginning to show its edge.

After the Limit of Heat, although the subtropical high withdrew to the south, it would never easily give up its dominance and easily retreat to the West Pacific Sea. In the southern areas controlled by it, often at the limit of heat, once again feel the high temperature weather, which is the short-term hot weather "autumn tiger". The length of the autumn tiger varies each year, generally lasting from half a month to two months. The reason for the formation of autumn tiger is that the Western Pacific Subtropical high, which controls China, gradually moves southward in autumn, but then rises northward. Under the control of the subtropical high, it is clear and less cloudy, the sunshine is strong, and the temperature rises.

Thunderstorm activity after Limit of Heat is not as active as in hot summer, and the overall trend of heavy rain across the country is weakened. During Limit of Heat, the rainfall distribution in South China changes from more in the west to less in the east to more in the east. Southwest and West China, because of the subtropical high edge, coupled with the role of mountains, thunderstorms are more active. In September, most of China begins to enter the period of low rainfall, and the autumn rain is more in West China, which is a special weather phenomenon in autumn in western China. Under the control of cold high pressure, sinking, dry cold air is formed, and the rainy season (" seven down and eight up ") in Northeast, North and Northwest China is over.