When does the rainy season usually occur?

In my country, the rainy season in the south is from April to September, and in the north from July to August.

The rainy season refers to the season in a year when precipitation is relatively concentrated, that is, the humid and rainy season when precipitation is relatively concentrated every year. my country's precipitation is mainly brought by the southeast monsoon. Therefore, my country's precipitation shows the characteristic of "decreasing from the southeast coast to the northwest inland" in geographical space.