Why is the weather in Changsha hot and cold?

Just a few days ago, I had a short day in Changsha. I have experienced it all year round, spring, summer, autumn and winter. In the morning, the temperature is not high, it is cool and there is a little light rain (spring). After 10, the temperature began to rise to about 30 degrees at noon (summer). In the afternoon, the temperature began to drop, and at dusk 10 degrees, but the weather was quite good (autumn).